# MacOS Techniques

NameTacticsIDTechnical Description
.bash_profile and .bashrcPersistenceT1156~/.bash_profile and ~/.bashrc are executed in a user's context when a new shell opens or when a user logs in so that their environment is set correctly. ~/.bash_profile is executed for login shells and ~/.bashrc is executed for interactive non-login shells. This means that when a user logs in (via username and password) to the console (either locally or remotely via something like SSH), ~/.bash_profile is executed before the initial command prompt is returned to the user. After that, every time a new shell is opened, ~/.bashrc is executed. This allows users more fine grained control over when they want certain commands executed.

Mac's Terminal.app is a little different in that it runs a login shell by default each time a new terminal window is opened, thus calling ~/.bash_profile each time instead of ~/.bashrc.

These files are meant to be written to by the local user to configure their own environment; however, adversaries can also insert code into these files to gain persistence each time a user logs in or opens a new shell.
Account DiscoveryDiscoveryT1087Adversaries may attempt to get a listing of local system or domain accounts.

### Windows

Example commands that can acquire this information are net user, net group <groupname>, and net localgroup <groupname> using the Net utility or through use of dsquery. If adversaries attempt to identify the primary user, currently logged in user, or set of users that commonly uses a system, System Owner/User Discovery may apply.

### Mac

On Mac, groups can be enumerated through the groups and id commands. In mac specifically, dscl . list /Groups and dscacheutil -q group can also be used to enumerate groups and users.

### Linux

On Linux, local users can be enumerated through the use of the /etc/passwd file which is world readable. In mac, this same file is only used in single-user mode in addition to the /etc/master.passwd file.

Also, groups can be enumerated through the groups and id commands. In mac specifically, dscl . list /Groups and dscacheutil -q group can also be used to enumerate groups and users.
AppleScriptExecution
Lateral Movement
T1155macOS and OS X applications send AppleEvent messages to each other for interprocess communications (IPC). These messages can be easily scripted with AppleScript for local or remote IPC. Osascript executes AppleScript and any other Open Scripting Architecture (OSA) language scripts. A list of OSA languages installed on a system can be found by using the osalang program.

AppleEvent messages can be sent independently or as part of a script. These events can locate open windows, send keystrokes, and interact with almost any open application locally or remotely.

Adversaries can use this to interact with open SSH connection, move to remote machines, and even present users with fake dialog boxes. These events cannot start applications remotely (they can start them locally though), but can interact with applications if they're already running remotely. Since this is a scripting language, it can be used to launch more common techniques as well such as a reverse shell via python 1. Scripts can be run from the command lie via osascript /path/to/script or osascript -e "script here".
Application Deployment SoftwareLateral MovementT1017Adversaries may deploy malicious software to systems within a network using application deployment systems employed by enterprise administrators. The permissions required for this action vary by system configuration; local credentials may be sufficient with direct access to the deployment server, or specific domain credentials may be required. However, the system may require an administrative account to log in or to perform software deployment. Access to a network-wide or enterprise-wide software deployment system enables an adversary to have remote code execution on all systems that are connected to such a system. The access may be used to laterally move to systems, gather information, or cause a specific effect, such as wiping the hard drives on all endpoints.
Application Window DiscoveryDiscoveryT1010Adversaries may attempt to get a listing of open application windows. Window listings could convey information about how the system is used or give context to information collected by a keylogger. In Mac, this can be done natively with a small AppleScript script.
Audio CaptureCollectionT1123An adversary can leverage a computer's peripheral devices (e.g., microphones and webcams) or applications (e.g., voice and video call services) to capture audio recordings for the purpose of listening into sensitive conversations to gather information. Malware or scripts may be used to interact with the devices through an available API provided by the operating system or an application to capture audio. Audio files may be written to disk and exfiltrated later.
Automated CollectionCollectionT1119Once established within a system or network, an adversary may use automated techniques for collecting internal data. Methods for performing this technique could include use of Scripting to search for and copy information fitting set criteria such as file type, location, or name at specific time intervals. This functionality could also be built into remote access tools. This technique may incorporate use of other techniques such as File and Directory Discovery and Remote File Copy to identify and move files.
Automated ExfiltrationExfiltrationT1020Data, such as sensitive documents, may be exfiltrated through the use of automated processing or Scripting after being gathered during Collection. When automated exfiltration is used, other exfiltration techniques likely apply as well to transfer the information out of the network, such as Exfiltration Over Command and Control Channel and Exfiltration Over Alternative Protocol.
Bash HistoryCredential AccessT1139Bash keeps track of the commands users type on the command-line with the "history" utility. Once a user logs out, the history is flushed to the user’s .bash_history file. For each user, this file resides at the same location: ~/.bash_history. Typically, this file keeps track of the user’s last 500 commands. Users often type usernames and passwords on the command-line as parameters to programs, which then get saved to this file when they log out. Attackers can abuse this by looking through the file for potential credentials.2
Binary PaddingDefense EvasionT1009Some security tools inspect files with static signatures to determine if they are known malicious. Adversaries may add data to files to increase the size beyond what security tools are capable of handling or to change the file hash to avoid hash-based blacklists.
Browser ExtensionsCollection
Persistence
T1176Browser extensions or plugins are small programs that can add functionality and customize aspects of internet browsers. They can be installed directly or through a browser's app store. Extensions generally have access and permissions to everything that the browser can access.34 Malicious extensions can be installed into a browser through malicious app store downloads masquerading as legitimate extensions, through social engineering, or by an adversary that has already compromised a system. Security can be limited on browser app stores so may not be difficult for malicious extensions to defeat automated scanners and be uploaded.5 Once the extension is installed, it can browse to websites in the background,67 steal all information that a user enters into a browser, to include credentials,89 and be used as an installer for a RAT for persistence. There have been instances of botnets using a persistent backdoor through malicious Chrome extensions.10 There have also been similar examples of extensions being used for command & control 11.

Credential Dumping to obtain password hashes may only get an adversary so far when Pass the Hash is not an option. Techniques to systematically guess the passwords used to compute hashes are available, or the adversary may use a pre-computed rainbow table. Cracking hashes is usually done on adversary-controlled systems outside of the target network.12

Adversaries may attempt to brute force logins without knowledge of passwords or hashes during an operation either with zero knowledge or by attempting a list of known or possible passwords. This is a riskier option because it could cause numerous authentication failures and account lockouts, depending on the organization's login failure policies.13

A related technique called password spraying uses one password, or a small list of passwords, that matches the complexity policy of the domain and may be a commonly used password. Logins are attempted with that password and many different accounts on a network to avoid account lockouts that would normally occur when brute forcing a single account with many passwords.14
Clear Command HistoryDefense EvasionT1146macOS and Linux both keep track of the commands users type in their terminal so that users can easily remember what they've done. These logs can be accessed in a few different ways. While logged in, this command history is tracked in a file pointed to by the environment variable HISTFILE. When a user logs off a system, this information is flushed to a file in the user's home directory called ~/.bash_history. The benefit of this is that it allows users to go back to commands they've used before in different sessions. Since everything typed on the command-line is saved, passwords passed in on the command line are also saved. Adversaries can abuse this by searching these files for cleartext passwords. Additionally, adversaries can use a variety of methods to prevent their own commands from appear in these logs such as unset HISTFILE, export HISTFILESIZE=0, history -c, rm ~/.bash_history.
Clipboard DataCollectionT1115Adversaries may collect data stored in the Windows clipboard from users copying information within or between applications.

### Windows

Applications can access clipboard data by using the Windows API.15

### Mac

OSX provides a native command, pbpaste, to grab clipboard contents 16.
Code SigningDefense EvasionT1116Code signing provides a level of authenticity on a binary from the developer and a guarantee that the binary has not been tampered with.17 However, adversaries are known to use code signing certificates to masquerade malware and tools as legitimate binaries18. The certificates used during an operation may be created, forged, or stolen by the adversary.1920

Code signing to verify software on first run can be used on modern Windows and macOS/OS X systems. It is not used on Linux due to the decentralized nature of the platform.17

Code signing certificates may be used to bypass security policies that require signed code to execute on a system.
Command-Line InterfaceExecutionT1059Command-line interfaces provide a way of interacting with computer systems and is a common feature across many types of operating system platforms.21 One example command-line interface on Windows systems is cmd, which can be used to perform a number of tasks including execution of other software. Command-line interfaces can be interacted with locally or remotely via a remote desktop application, reverse shell session, etc. Commands that are executed run with the current permission level of the command-line interface process unless the command includes process invocation that changes permissions context for that execution (e.g. Scheduled Task). Adversaries may use command-line interfaces to interact with systems and execute other software during the course of an operation.
Commonly Used PortCommand and ControlT1043Adversaries may communicate over a commonly used port to bypass firewalls or network detection systems and to blend with normal network activity to avoid more detailed inspection. They may use commonly open ports such as
• TCP:80 (HTTP)
• TCP:443 (HTTPS)
• TCP:25 (SMTP)
• TCP/UDP:53 (DNS)

They may use the protocol associated with the port or a completely different protocol.

For connections that occur internally within an enclave (such as those between a proxy or pivot node and other nodes), examples of common ports are

• TCP/UDP:135 (RPC)
• TCP/UDP:22 (SSH)
• TCP/UDP:3389 (RDP)
Communication Through Removable MediaCommand and ControlT1092Adversaries can perform command and control between compromised hosts on potentially disconnected networks using removable media to transfer commands from system to system. Both systems would need to be compromised, with the likelihood that an Internet-connected system was compromised first and the second through lateral movement by Replication Through Removable Media. Commands and files would be relayed from the disconnected system to the Internet-connected system to which the adversary has direct access.
Connection ProxyCommand and ControlT1090A connection proxy is used to direct network traffic between systems or act as an intermediary for network communications. Many tools exist that enable traffic redirection through proxies or port redirection, including HTRAN, ZXProxy, and ZXPortMap.22

The definition of a proxy can also be expanded out to encompass trust relationships between networks in peer-to-peer, mesh, or trusted connections between networks consisting of hosts or systems that regularly communicate with each other.

The network may be within a single organization or across organizations with trust relationships. Adversaries could use these types of relationships to manage command and control communications, to reduce the number of simultaneous outbound network connections, to provide resiliency in the face of connection loss, or to ride over existing trusted communications paths between victims to avoid suspicion.
Create AccountPersistenceT1136Adversaries with a sufficient level of access may create a local system or domain account. Such accounts may be used for persistence that do not require persistent remote access tools to be deployed on the system. The net user commands can be used to create a local or domain account.
Credentials in FilesCredential AccessT1081Adversaries may search local file systems and remote file shares for files containing passwords. These can be files created by users to store their own credentials, shared credential stores for a group of individuals, configuration files containing passwords for a system or service, or source code/binary files containing embedded passwords. It is possible to extract passwords from backups or saved virtual machines through Credential Dumping.23 Passwords may also be obtained from Group Policy Preferences stored on the Windows Domain Controller.24
Custom Command and Control ProtocolCommand and ControlT1094Adversaries may communicate using a custom command and control protocol instead of using existing Standard Application Layer Protocol to encapsulate commands. Implementations could mimic well-known protocols.
Custom Cryptographic ProtocolCommand and ControlT1024Adversaries may use a custom cryptographic protocol or algorithm to hide command and control traffic. A simple scheme, such as XOR-ing the plaintext with a fixed key, will produce a very weak ciphertext.

Custom encryption schemes may vary in sophistication. Analysis and reverse engineering of malware samples may be enough to discover the algorithm and encryption key used.

Some adversaries may also attempt to implement their own version of a well-known cryptographic algorithm instead of using a known implementation library, which may lead to unintentional errors.25
Data CompressedExfiltrationT1002An adversary may compress data (e.g., sensitive documents) that is collected prior to exfiltration in order to make it portable and minimize the amount of data sent over the network. The compression is done separately from the exfiltration channel and is performed using a custom program or algorithm, or a more common compression library or utility such as 7zip, RAR, ZIP, or zlib.
Data EncodingCommand and ControlT1132Command and control (C2) information is encoded using a standard data encoding system. Use of data encoding may be to adhere to existing protocol specifications and includes use of ASCII, Unicode, Base64, MIME, UTF-8, or other binary-to-text and character encoding systems.2627 Some data encoding systems may also result in data compression, such as gzip.
Data EncryptedExfiltrationT1022Data is encrypted before being exfiltrated in order to hide the information that is being exfiltrated from detection or to make the exfiltration less conspicuous upon inspection by a defender. The encryption is performed by a utility, programming library, or custom algorithm on the data itself and is considered separate from any encryption performed by the command and control or file transfer protocol. Common file archive formats that can encrypt files are RAR and zip. Other exfiltration techniques likely apply as well to transfer the information out of the network, such as Exfiltration Over Command and Control Channel and Exfiltration Over Alternative Protocol
Data ObfuscationCommand and ControlT1001Command and control (C2) communications are hidden (but not necessarily encrypted) in an attempt to make the content more difficult to discover or decipher and to make the communication less conspicuous and hide commands from being seen. This encompasses many methods, such as adding junk data to protocol traffic, using steganography, commingling legitimate traffic with C2 communications traffic, or using a non-standard data encoding system, such as a modified Base64 encoding for the message body of an HTTP request.
Data StagedCollectionT1074Collected data is staged in a central location or directory prior to Exfiltration. Data may be kept in separate files or combined into one file through techniques such as Data Compressed or Data Encrypted. Interactive command shells may be used, and common functionality within cmd and bash may be used to copy data into a staging location.
Data Transfer Size LimitsExfiltrationT1030An adversary may exfiltrate data in fixed size chunks instead of whole files or limit packet sizes below certain thresholds. This approach may be used to avoid triggering network data transfer threshold alerts.
Data from Local SystemCollectionT1005Sensitive data can be collected from local system sources, such as the file system or databases of information residing on the system prior to Exfiltration. Adversaries will often search the file system on computers they have compromised to find files of interest. They may do this using a Command-Line Interface, such as cmd, which has functionality to interact with the file system to gather information. Some adversaries may also use Automated Collection on the local system.
Data from Network Shared DriveCollectionT1039Sensitive data can be collected from remote systems via shared network drives (host shared directory, network file server, etc.) that are accessible from the current system prior to Exfiltration. Adversaries may search network shares on computers they have compromised to find files of interest. Interactive command shells may be in use, and common functionality within cmd may be used to gather information.
Data from Removable MediaCollectionT1025Sensitive data can be collected from any removable media (optical disk drive, USB memory, etc.) connected to the compromised system prior to Exfiltration. Adversaries may search connected removable media on computers they have compromised to find files of interest. Interactive command shells may be in use, and common functionality within cmd may be used to gather information. Some adversaries may also use Automated Collection on removable media.
Disabling Security ToolsDefense EvasionT1089Adversaries may disable security tools to avoid possible detection of their tools and activities. This can take the form of killing security software or event logging processes, deleting Registry keys so that tools do not start at run time, or other methods to interfere with security scanning or event reporting.
Domain FrontingCommand and ControlT1172Domain fronting takes advantage of routing schemes in Content Delivery Networks (CDNs) and other services which host multiple domains to obfuscate the intended destination of HTTPS traffic or traffic tunneled through HTTPS.28 The technique involves using different domain names in the SNI field of the TLS header and the Host field of the HTTP header. If both domains are served from the same CDN, then the CDN may route to the address specified in the HTTP header after unwrapping the TLS header. A variation of the the technique, "domainless" fronting, utilizes a SNI field that is left blank; this may allow the fronting to work even when the CDN attempts to validate that the SNI and HTTP Host fields match (if the blank SNI fields are ignored). For example, if domain-x and domain-y are customers of the same CDN, it is possible to place domain-x in the TLS header and domain-y in the HTTP header. Traffic will appear to be going to domain-x, however the CDN may route it to domain-y.
Dylib HijackingPersistence
Privilege Escalation
T1157macOS and OS X use a common method to look for required dynamic libraries (dylib) to load into a program based on search paths. Adversaries can take advantage of ambiguous paths to plant dylibs to gain privilege escalation or persistence.

A common method is to see what dylibs an application uses, then plant a malicious version with the same name higher up in the search path. This typically results in the dylib being in the same folder as the application itself.2930

If the program is configured to run at a higher privilege level than the current user, then when the dylib is loaded into the application, the dylib will also run at that elevated level. This can be used by adversaries as a privilege escalation technique.
Exfiltration Over Alternative ProtocolExfiltrationT1048Data exfiltration is performed with a different protocol from the main command and control protocol or channel. The data is likely to be sent to an alternate network location from the main command and control server. Alternate protocols include FTP, SMTP, HTTP/S, DNS, or some other network protocol. Different channels could include Internet Web services such as cloud storage.
Exfiltration Over Command and Control ChannelExfiltrationT1041Data exfiltration is performed over the Command and Control channel. Data is encoded into the normal communications channel using the same protocol as command and control communications.
Exfiltration Over Other Network MediumExfiltrationT1011Exfiltration could occur over a different network medium than the command and control channel. If the command and control network is a wired Internet connection, the exfiltration may occur, for example, over a WiFi connection, modem, cellular data connection, Bluetooth, or another radio frequency (RF) channel. Adversaries could choose to do this if they have sufficient access or proximity, and the connection might not be secured or defended as well as the primary Internet-connected channel because it is not routed through the same enterprise network.
Exfiltration Over Physical MediumExfiltrationT1052In certain circumstances, such as an air-gapped network compromise, exfiltration could occur via a physical medium or device introduced by a user. Such media could be an external hard drive, USB drive, cellular phone, MP3 player, or other removable storage and processing device. The physical medium or device could be used as the final exfiltration point or to hop between otherwise disconnected systems.
Exploitation of VulnerabilityCredential Access
Defense Evasion
Lateral Movement
Privilege Escalation
T1068Exploitation of a software vulnerability occurs when an adversary takes advantage of a programming error in a program, service, or within the operating system software or kernel itself to execute adversary-controlled code. Exploiting software vulnerabilities may allow adversaries to run a command or binary on a remote system for lateral movement, escalate a current process to a higher privilege level, or bypass security mechanisms. Exploits may also allow an adversary access to privileged accounts and credentials. One example of this is MS14-068, which can be used to forge Kerberos tickets using domain user permissions.3132
Fallback ChannelsCommand and ControlT1008Adversaries may use fallback or alternate communication channels if the primary channel is compromised or inaccessible in order to maintain reliable command and control and to avoid data transfer thresholds.
File DeletionDefense EvasionT1107Malware, tools, or other non-native files dropped or created on a system by an adversary may leave traces behind as to what was done within a network and how. Adversaries may remove these files over the course of an intrusion to keep their footprint low or remove them at the end as part of the post-intrusion cleanup process. There are tools available from the host operating system to perform cleanup, but adversaries may use other tools as well. Examples include native cmd functions such as DEL, secure deletion tools such as Windows Sysinternals SDelete, or other third-party file deletion tools.22
File and Directory DiscoveryDiscoveryT1083Adversaries may enumerate files and directories or may search in specific locations of a host or network share for certain information within a file system.

### Windows

Example utilities used to obtain this information are dir and tree.33 Custom tools may also be used to gather file and directory information and interact with the Windows API.

### Mac and Linux

In Mac and Linux, this kind of discovery is accomplished with the ls, find, and locate commands.
Gatekeeper BypassDefense EvasionT1144In macOS and OS X, when applications or programs are downloaded from the internet, there is a special attribute set on the file called com.apple.quarantine. This attribute is read by Apple's Gatekeeper defense program at execution time and provides a prompt to the user to allow or deny execution.

Apps loaded onto the system from USB flash drive, optical disk, external hard drive, or even from a drive shared over the local network won’t set this flag. Additionally, other utilities or events like drive-by downloads don’t necessarily set it either. This completely bypasses the built-in Gatekeeper check.34 The presence of the quarantine flag can be checked by the xattr command xattr /path/to/MyApp.app for com.apple.quarantine. Similarly, given sudo access or elevated permission, this attribute can be removed with xattr as well, sudo xattr -r -d com.apple.quarantine /path/to/MyApp.app.3536

In typical operation, a file will be downloaded from the internet and given a quarantine flag before being saved to disk. When the user tries to open the file or application, macOS’s gatekeeper will step in and check for the presence of this flag. If it exists, then macOS will then prompt the user to confirmation that they want to run the program and will even provide the URL where the application came from. However, this is all based on the file being downloaded from a quarantine-savvy application.37
Graphical User InterfaceExecutionT1061Cause a binary or script to execute based on interacting with the file through a graphical user interface (GUI) or in an interactive remote session such as Remote Desktop Protocol.
HISTCONTROLDefense EvasionT1148The HISTCONTROL environment variable keeps track of what should be saved by the history command and eventually into the ~/.bash_history file when a user logs out. This setting can be configured to ignore commands that start with a space by simply setting it to "ignorespace". HISTCONTROL can also be set to ignore duplicate commands by setting it to "ignoredups". In some Linux systems, this is set by default to "ignoreboth" which covers both of the previous examples. This means that “ ls” will not be saved, but “ls” would be saved by history. HISTCONTROL does not exist by default on macOS, but can be set by the user and will be respected. Adversaries can use this to operate without leaving traces by simply prepending a space to all of their terminal commands.
Hidden Files and DirectoriesDefense Evasion
Persistence
T1158To prevent normal users from accidentally changing special files on a system, most operating systems have the concept of a ‘hidden’ file. These files don’t show up when a user browses the file system with a GUI or when using normal commands on the command line. Users must explicitly ask to show the hidden files either via a series of Graphical User Interface (GUI) prompts or with command line switches (dir /a for Windows and ls –a for Linux and macOS).

### Windows

Users can mark specific files as hidden by using the attrib.exe binary. Simply do attrib +h filename to mark a file or folder as hidden. Similarly, the “+s” marks a file as a system file and the “+r” flag marks the file as read only. Like most windows binaries, the attrib.exe binary provides the ability to apply these changes recursively “/S”.

### Linux/Mac

Users can mark specific files as hidden simply by putting a “.” as the first character in the file or folder name 3839. Files and folder that start with a period, ‘.’, are by default hidden from being viewed in the Finder application and standard command-line utilities like “ls”. Users must specifically change settings to have these files viewable. For command line usages, there is typically a flag to see all files (including hidden ones). To view these files in the Finder Application, the following command must be executed: defaults write com.apple.finder AppleShowAllFiles YES, and then relaunch the Finder Application.

### Mac

Files on macOS can be marked with the UF_HIDDEN flag which prevents them from being seen in Finder.app, but still allows them to be seen in Terminal.app40. Many applications create these hidden files and folders to store information so that it doesn’t clutter up the user’s workspace. For example, SSH utilities create a .ssh folder that’s hidden and contains the user’s known hosts and keys.

Adversaries can use this to their advantage to hide files and folders anywhere on the system for persistence and evading a typical user or system analysis that does not incorporate investigation of hidden files.
Hidden UsersDefense EvasionT1147Every user account in macOS has a userID associated with it. When creating a user, you can specify the userID for that account. There is a property value in /Library/Preferences/com.apple.loginwindow called Hide500Users that prevents users with userIDs 500 and lower from appearing at the login screen. By using the Create Account technique with a userID under 500 and enabling this property (setting it to Yes), an adversary can hide their user accounts much more easily: sudo dscl . -create /Users/username UniqueID 40141.
Hidden WindowDefense EvasionT1143The configurations for how applications run on macOS and OS X are listed in property list (plist) files. One of the tags in these files can be apple.awt.UIElement, which allows for Java applications to prevent the application's icon from appearing in the Dock. A common use for this is when applications run in the system tray, but don't also want to show up in the Dock. However, adversaries can abuse this feature and hide their running window 39.
Indicator Removal from ToolsDefense EvasionT1066If a malicious tool is detected and quarantined or otherwise curtailed, an adversary may be able to determine why the malicious tool was detected (the indicator), modify the tool by removing the indicator, and use the updated version that is no longer detected by the target's defensive systems or subsequent targets that may use similar systems. A good example of this is when malware is detected with a file signature and quarantined by anti-virus software. An adversary who can determine that the malware was quarantined because of its file signature may use Software Packing or otherwise modify the file so it has a different signature, and then re-use the malware.
Indicator Removal on HostDefense EvasionT1070Adversaries may delete or alter generated event files on a host system, including potentially captured files such as quarantined malware. This may compromise the integrity of the security solution, causing events to go unreported, or make forensic analysis and incident response more difficult due to lack of sufficient data to determine what occurred.
Input CaptureCollection
Credential Access
T1056Adversaries can use methods of capturing user input for obtaining credentials for Valid Accounts and information Collection that include keylogging and user input field interception.

Keylogging is the most prevalent type of input capture, with many different ways of intercepting keystrokes,42 but other methods exist to target information for specific purposes, such as performing a UAC prompt or wrapping the Windows default credential provider.43

Keylogging is likely to be used to acquire credentials for new access opportunities when Credential Dumping efforts are not effective, and may require an adversary to remain passive on a system for a period of time before an opportunity arises.

Adversaries may also install code on externally facing portals, such as a VPN login page, to capture and transmit credentials of users who attempt to log into the service. This variation on input capture may be conducted post-compromise using legitimate administrative access as a backup measure to maintain network access through External Remote Services and Valid Accounts or as part of the initial compromise by exploitation of the externally facing web service.44
Input PromptCredential AccessT1141When programs are executed that need additional privileges than are present in the current user context, it is common for the operating system to prompt the user for proper credentials to authorize the elevated privileges for the task. Adversaries can mimic this functionality to prompt users for credentials with a normal-looking prompt. This type of prompt can be accomplished with AppleScript:

set thePassword to the text returned of (display dialog "AdobeUpdater needs permission to check for updates. Please authenticate." default answer "") 45

Adversaries can prompt a user for a number of reasons that mimic normal usage, such as a fake installer requiring additional access or a fake malware removal suite.46
KeychainCredential AccessT1142Keychains are the built-in way for macOS to keep track of users' passwords and credentials for many services and features such as WiFi passwords, websites, secure notes, certificates, and Kerberos. Keychain files are located in ~/Library/Keychains/,/Library/Keychains/, and /Network/Library/Keychains/.47 The security command-line utility, which is built into macOS by default, provides a useful way to manage these credentials. To manage their credentials, users have to use additional credentials to access their keychain. If an adversary knows the credentials for the login keychain, then they can get access to all the other credentials stored in this vault.2 By default, the passphrase for the keychain is the user’s logon credentials.
LC_MAIN HijackingDefense EvasionT1149As of OS X 10.8, mach-O binaries introduced a new header called LC_MAIN that points to the binary’s entry point for execution. Previously, there were two headers to achieve this same effect: LC_THREAD and LC_UNIXTHREAD 48. The entry point for a binary can be hijacked so that initial execution flows to a malicious addition (either another section or a code cave) and then goes back to the initial entry point so that the victim doesn’t know anything was different 34. By modifying a binary in this way, application whitelisting can be bypassed because the file name or application path is still the same.
Launch AgentPersistenceT1159Per Apple’s developer documentation, when a user logs in, a per-user launchd process is started which loads the parameters for each launch-on-demand user agent from the property list (plist) files found in /System/Library/LaunchAgents, /Library/LaunchAgents, and \$HOME/Library/LaunchAgents494539. These launch agents have property list files which point to the executables that will be launched50. Adversaries may install a new launch agent that can be configured to execute at login by using launchd or launchctl to load a plist into the appropriate directories 38 34. The agent name may be disguised by using a name from a related operating system or benign software. Launch Agents are created with user level privileges and are executed with the privileges of the user when they log in5136. They can be set up to execute when a specific user logs in (in the specific user’s directory structure) or when any user logs in (which requires administrator privileges).
Launch DaemonPersistence
Privilege Escalation
T1160Per Apple’s developer documentation, when macOS and OS X boot up, launchd is run to finish system initialization. This process loads the parameters for each launch-on-demand system-level daemon from the property list (plist) files found in /System/Library/LaunchDaemons and /Library/LaunchDaemons49. These LaunchDaemons have property list files which point to the executables that will be launched34.

Adversaries may install a new launch daemon that can be configured to execute at startup by using launchd or launchctl to load a plist into the appropriate directories51. The daemon name may be disguised by using a name from a related operating system or benign software 40. Launch Daemons may be created with administrator privileges, but are executed under root privileges, so an adversary may also use a service to escalate privileges from administrator to root.

The plist file permissions must be root:wheel, but the script or program that it points to has no such requirement. So, it is possible for poor configurations to allow an adversary to modify a current Launch Daemon’s executable and gain persistence or Privilege Escalation.
LaunchctlDefense Evasion
Execution
Persistence
T1152Launchctl controls the macOS launchd process which handles things like launch agents and launch daemons, but can execute other commands or programs itself. Launchctl supports taking subcommands on the command-line, interactively, or even redirected from standard input. By loading or reloading launch agents or launch daemons, adversaries can install persistence or execute changes they made 38. Running a command from launchctl is as simple as launchctl submit -l <labelName> -- /Path/to/thing/to/execute "arg" "arg" "arg". Loading, unloading, or reloading launch agents or launch daemons can require elevated privileges. Adversaries can abuse this functionality to execute code or even bypass whitelisting if launchctl is an allowed process.
Local Job SchedulingPersistence
Execution
T1168On Linux and Apple systems, multiple methods are supported for creating pre-scheduled and periodic background jobs: cron,52 at,53 and launchd.54 Unlike Scheduled Task on Windows systems, job scheduling on Linux-based systems cannot be done remotely unless used in conjunction within an established remote session, like secure shell (SSH).

### cron

System-wide cron jobs are installed by modifying /etc/crontab file, /etc/cron.d/ directory or other locations supported by the Cron daemon, while per-user cron jobs are installed using crontab with specifically formatted crontab files.54 This works on Mac and Linux systems.

Those methods allow for commands or scripts to be executed at specific, periodic intervals in the background without user interaction. An adversary may use job scheduling to execute programs at system startup or on a scheduled basis for Persistence,18343055 to conduct Execution as part of Lateral Movement, to gain root privileges, or to run a process under the context of a specific account.

### at

The at program is another means on Linux-based systems, including Mac, to schedule a program or script job for execution at a later date and/or time, which could also be used for the same purposes.

### launchd

Each launchd job is described by a different configuration property list (plist) file similar to Launch Daemon or Launch Agent, except there is an additional key called StartCalendarInterval with a dictionary of time values.54 This only works on macOS and OS X.
Login ItemPersistenceT1162MacOS provides the option to list specific applications to run when a user logs in. These applications run under the logged in user's context, and will be started every time the user logs in. Login items installed using the Service Management Framework are not visible in the System Preferences and can only be removed by the application that created them56. Users have direct control over login items installed using a shared file list which are also visible in System Preferences56. These login items are stored in the user's ~/Library/Preferences/ directory in a plist file called com.apple.loginitems.plist34. Some of these applications can open visible dialogs to the user, but they don’t all have to since there is an option to ‘Hide’ the window. If an adversary can register their own login item or modified an existing one, then they can use it to execute their code for a persistence mechanism each time the user logs in3050.
Logon ScriptsLateral Movement
Persistence
T1037===Windows===

Windows allows logon scripts to be run whenever a specific user or group of users log into a system.57 The scripts can be used to perform administrative functions, which may often execute other programs or send information to an internal logging server.

If adversaries can access these scripts, they may insert additional code into the logon script to execute their tools when a user logs in. This code can allow them to maintain persistence on a single system, if it is a local script, or to move laterally within a network, if the script is stored on a central server and pushed to many systems. Depending on the access configuration of the logon scripts, either local credentials or an administrator account may be necessary.

### Mac

Mac allows login and logoff hooks to be run as root whenever a specific user logs into or out of a system. A login hook tells Mac OS X to execute a certain script when a user logs in, but unlike startup items, a login hook executes as root58. There can only be one login hook at a time though. If adversaries can access these scripts, they can insert additional code to the script to execute their tools when a user logs in.
MasqueradingDefense EvasionT1036Masquerading occurs when the name or location of an executable, legitimate or malicious, is manipulated or abused for the sake of evading defenses and observation. Several different variations of this technique have been observed.

One variant is for an executable to be placed in a commonly trusted directory or given the name of a legitimate, trusted program. Alternatively, the filename given may be a close approximation of legitimate programs. This is done to bypass tools that trust executables by relying on file name or path, as well as to deceive defenders and system administrators into thinking a file is benign by associating the name with something that is thought to be legitimate.

### Windows

In another variation of this technique, an adversary may use a renamed copy of a legitimate utility, such as rundll32.exe.59 An alternative case occurs when a legitimate utility is moved to a different directory and also renamed to avoid detections based on system utilities executing from non-standard paths.60

An example of abuse of trusted locations in Windows would be the C:\Windows\System32 directory. Examples of trusted binary names that can be given to malicious binares include "explorer.exe" and "svchost.exe".

### Linux

Another variation of this technique includes malicious binaries changing the name of their running process to that of a trusted or benign process, after they have been launched as opposed to before. 61

An example of abuse of trusted locations in Linux would be the /bin directory. Examples of trusted binary names that can be given to malicious binares include "rsyncd" and "dbus-inotifier". 62 63
Multi-Stage ChannelsCommand and ControlT1104Adversaries may create multiple stages for command and control that are employed under different conditions or for certain functions. Use of multiple stages may obfuscate the command and control channel to make detection more difficult.

Remote access tools will call back to the first-stage command and control server for instructions. The first stage may have automated capabilities to collect basic host information, update tools, and upload additional files. A second remote access tool (RAT) could be uploaded at that point to redirect the host to the second-stage command and control server. The second stage will likely be more fully featured and allow the adversary to interact with the system through a reverse shell and additional RAT features.

The different stages will likely be hosted separately with no overlapping infrastructure. The loader may also have backup first-stage callbacks or Fallback Channels in case the original first-stage communication path is discovered and blocked.
Multi-hop ProxyCommand and ControlT1188To disguise the source of malicious traffic, adversaries may chain together multiple proxies. Typically, a defender will be able to identify the last proxy traffic traversed before it enters their network; the defender may or may not be able to identify any previous proxies before the last-hop proxy. This technique makes identifying the original source of the malicious traffic even more difficult by requiring the defender to trace malicious traffic through several proxies to identify its source.
Multiband CommunicationCommand and ControlT1026Some adversaries may split communications between different protocols. There could be one protocol for inbound command and control and another for outbound data, allowing it to bypass certain firewall restrictions. The split could also be random to simply avoid data threshold alerts on any one communication.
Multilayer EncryptionCommand and ControlT1079An adversary performs C2 communications using multiple layers of encryption, typically (but not exclusively) tunneling a custom encryption scheme within a protocol encryption scheme such as HTTPS or SMTPS.
Network Service ScanningDiscoveryT1046Adversaries may attempt to get a listing of services running on remote hosts, including those that may be vulnerable to remote software exploitation. Methods to acquire this information include port scans and vulnerability scans using tools that are brought onto a system.
Network Share DiscoveryDiscoveryT1135Networks often contain shared network drives and folders that enable users to access file directories on various systems across a network.

### Windows

File sharing over a Windows network occurs over the SMB protocol.6465

Net can be used to query a remote system for available shared drives using the net view \\remotesystem command. It can also be used to query shared drives on the local system using net share.

Adversaries may look for folders and drives shared on remote systems as a means of identifying sources of information to gather as a precursor for Collection and to identify potential systems of interest for Lateral Movement.

### Mac

On Mac, locally mounted shares can be viewed with the df -aH command.
Network SniffingCredential AccessT1040Network sniffing refers to using the network interface on a system to monitor or capture information sent over a wired or wireless connection. User credentials may be sent over an insecure, unencrypted protocol that can be captured and obtained through network packet analysis. An adversary may place a network interface into promiscuous mode, using a utility to capture traffic in transit over the network or use span ports to capture a larger amount of data. In addition, techniques for name service resolution poisoning, such as LLMNR/NBT-NS Poisoning, can be used to capture credentials to websites, proxies, and internal systems by redirecting traffic to an adversary.
Obfuscated Files or InformationDefense EvasionT1027Adversaries may attempt to make an executable or file difficult to discover or analyze by encrypting, encoding, or otherwise obfuscating its contents on the system. This is common behavior that can be used across different platforms to evade defenses. Portions of files can also be encoded to hide the plain-text strings that would otherwise help defenders with discovery.66
Permission Groups DiscoveryDiscoveryT1069Adversaries may attempt to find local system or domain-level groups and permissions settings.

### Windows

Examples of commands that can list groups are net group /domain and net localgroup using the Net utility.

### Mac

On Mac, this same thing can be accomplished with the dscacheutil -q group for the domain, or dscl . -list /Groups for local groups.

### Linux

On Linux, local groups can be enumerated with the groups command and domain groups via the ldapsearch command.
Plist ModificationDefense Evasion
Persistence
Privilege Escalation
T1150Property list (plist) files contain all of the information that macOS and OS X uses to configure applications and services. These files are UT-8 encoded and formatted like XML documents via a series of keys surrounded by < >. They detail when programs should execute, file paths to the executables, program arguments, required OS permissions, and many others. plists are located in certain locations depending on their purpose such as /Library/Preferences (which execute with elevated privileges) and ~/Library/Preferences (which execute with a user's privileges). Adversaries can modify these plist files to point to their own code, can use them to execute their code in the context of another user, bypass whitelisting procedures, or even use them as a persistence mechanism.38
Private KeysCredential AccessT1145Private cryptographic keys and certificates are used for authentication, encryption/decryption, and digital signatures.67

Adversaries may gather private keys from compromised systems for use in authenticating to Remote Services like SSH or for use in decrypting other collected files such as email. Common key and certificate file extensions include: .key, .pgp, .gpg, .ppk., .p12, .pem, pfx, .cer, .p7b, .asc. Adversaries may also look in common key directories, such as ~/.ssh for SSH keys on *nix-based systems or C:\Users\(username)\.ssh\ on Windows.

Private keys should require a password or passphrase for operation, so an adversary may also use Input Capture for keylogging or attempt to Brute Force the passphrase off-line.

Adversary tools have been discovered that search compromised systems for file extensions relating to cryptographic keys and certificates.6869
Process DiscoveryDiscoveryT1057Adversaries may attempt to get information about running processes on a system. Information obtained could be used to gain an understanding of common software running on systems within the network.

### Windows

An example command that would obtain details on processes is "tasklist" using the Tasklist utility.

### Mac and Linux

In Mac and Linux, this is accomplished with the ps command.
Process InjectionDefense Evasion
Privilege Escalation
T1055Process injection is a method of executing arbitrary code in the address space of a separate live process. Running code in the context of another process may allow access to the process's memory, system/network resources, and possibly elevated privileges. Execution via process injection may also evade detection from security products since the execution is masked under a legitimate process.

### Windows

There are multiple approaches to injecting code into a live process. Windows implementations include:70

• Dynamic-link library (DLL) injection involves writing the path to a malicious DLL inside a process then invoking execution by creating a remote thread.
• Portable executable injection involves writing malicious code directly into the process (without a file on disk) then invoking execution with either additional code or by creating a remote thread. The displacement of the injected code introduces the additional requirement for functionality to remap memory references. Variations of this method such as reflective DLL injection (writing a self-mapping DLL into a process) and memory module (map DLL when writing into process) overcome the address relocation issue.71
• Thread execution hijacking involves injecting malicious code or the path to a DLL into a thread of a process. Similar to Process Hollowing, the thread must first be suspended.
• Asynchronous Procedure Call (APC) injection involves attaching malicious code to the APC Queue72 of a process's thread. Queued APC functions are executed when the thread enters an alterable state. AtomBombing 73 is a variation that utilizes APCs to invoke malicious code previously written to the global atom table.74
• Thread Local Storage (TLS) callback injection involves manipulating pointers inside a portable executable (PE) to redirect a process to malicious code before reaching the code's legitimate entry point.75

### Mac and Linux

Implementations for Linux and OS X/macOS systems include:7677

• LD_PRELOAD, LD_LIBRARY_PATH (Linux), DYLD_INSERT_LIBRARIES (Mac OS X) environment variables, or the dlfcn application programming interface (API) can be used to dynamically load a library (shared object) in a process which can be used to intercept API calls from the running process.78
• Ptrace system calls can be used to attach to a running process and modify it in runtime.77
• /proc/[pid]/mem provides access to the memory of the process and can be used to read/write arbitrary data to it. This technique is very rare due to its complexity.77
• VDSO hijacking performs runtime injection on ELF binaries by manipulating code stubs mapped in from the linux-vdso.so shared object.79
Malware commonly utilizes process injection to access system resources through which Persistence and other environment modifications can be made. More sophisticated samples may perform multiple process injections to segment modules and further evade detection, utilizing named pipes or other inter-process communication (IPC) mechanisms as a communication channel.
Rc.commonPersistenceT1163During the boot process, macOS and Linux both execute source /etc/rc.common, which is a shell script containing various utility functions. This file also defines routines for processing command-line arguments and for gathering system settings, and is thus recommended to include in the start of Startup Item Scripts80. In macOS and OS X, this is now a deprecated technique in favor of launch agents and launch daemons, but is currently still used. Adversaries can use the rc.common file as a way to hide code for persistence that will execute on each reboot as the root user34.
Re-opened ApplicationsPersistenceT1164Starting in Mac OS X 10.7 (Lion), users can specify certain applications to be re-opened when a user reboots their machine. While this is usually done via a Graphical User Interface (GUI) on an app-by-app basis, there are property list files (plist) that contain this information as well located at ~/Library/Preferences/com.apple.loginwindow.plist and ~/Library/Preferences/ByHost/com.apple.loginwindow.*.plist. An adversary can modify one of these files directly to include a link to their malicious executable to provide a persistence mechanism each time the user reboots their machine34.
Redundant AccessDefense Evasion
Persistence
Remote File CopyCommand and Control
Lateral Movement
T1105Files may be copied from one system to another to stage adversary tools or other files over the course of an operation. Files may be copied from an external adversary-controlled system through the Command and Control channel to bring tools into the victim network or through alternate protocols with another tool such as FTP. Files can also be copied over on Mac and Linux with native tools like scp, rsync, and sftp. Adversaries may also copy files laterally between internal victim systems to support Lateral Movement with remote Execution using inherent file sharing protocols such as file sharing over SMB to connected network shares or with authenticated connections with Windows Admin Shares or Remote Desktop Protocol.
Remote ServicesLateral MovementT1021An adversary may use Valid Accounts to log into a service specifically designed to accept remote connections, such as telnet, SSH, and VNC. The adversary may then perform actions as the logged-on user.
Remote System DiscoveryDiscoveryT1018Adversaries will likely attempt to get a listing of other systems by IP address, hostname, or other logical identifier on a network that may be used for Lateral Movement from the current system. Functionality could exist within remote access tools to enable this, but utilities available on the operating system could also be used.

### Windows

Examples of tools and commands that acquire this information include "ping" or "net view" using Net.

### Mac

Specific to Mac, the bonjour protocol to discover additional Mac-based systems within the same broadcast domain. Utilities such as "ping" and others can be used to gather information about remote systems.

### Linux

Utilities such as "ping" and others can be used to gather information about remote systems.
RootkitDefense EvasionT1014Rootkits are programs that hide the existence of malware by intercepting (i.e., Hooking) and modifying operating system API calls that supply system information.82 Rootkits or rootkit enabling functionality may reside at the user or kernel level in the operating system or lower, to include a Hypervisor, Master Boot Record, or the System Firmware.83 Adversaries may use rootkits to hide the presence of programs, files, network connections, services, drivers, and other system components. Rootkits have been seen for Windows, Linux, and Mac OS X systems.8485
SSH HijackingLateral MovementT1184Secure Shell (SSH) is a standard means of remote access on Linux and Mac systems. It allows a user to connect to another system via an encrypted tunnel, commonly authenticating through a password, certificate or the use of an asymmetric encryption key pair.

In order to move laterally from a compromised host, adversaries may take advantage of trust relationships established with other systems via public key authentication in active SSH sessions by hijacking an existing connection to another system. This may occur through compromising the SSH agent itself or by having access to the agent's socket. If an adversary is able to obtain root access, then hijacking SSH sessions is likely trivial.868788 Compromising the SSH agent also provides access to intercept SSH credentials.89

SSH Hijacking differs from use of Remote Services because it injects into an existing SSH session rather than creating a new session using Valid Accounts.
Scheduled TransferExfiltrationT1029Data exfiltration may be performed only at certain times of day or at certain intervals. This could be done to blend traffic patterns with normal activity or availability. When scheduled exfiltration is used, other exfiltration techniques likely apply as well to transfer the information out of the network, such as Exfiltration Over Command and Control Channel and Exfiltration Over Alternative Protocol.
Screen CaptureCollectionT1113Adversaries may attempt to take screen captures of the desktop to gather information over the course of an operation. Screen capturing functionality may be included as a feature of a remote access tool used in post-compromise operations.

### Mac

On OSX, the native command screencapture is used to capture screenshots.

### Linux

On Linux, there is the native command xwd.39
ScriptingDefense Evasion
Execution
T1064Adversaries may use scripts to aid in operations and perform multiple actions that would otherwise be manual. Scripting is useful for speeding up operational tasks and reducing the time required to gain access to critical resources. Some scripting languages may be used to bypass process monitoring mechanisms by directly interacting with the operating system at an API level instead of calling other programs. Common scripting languages for Windows include VBScript and PowerShell but could also be in the form of command-line batch scripts. Many popular offensive frameworks exist which use forms of scripting for security testers and adversaries alike. Metasploit90, Veil91, and PowerSploit92 are three examples that are popular among penetration testers for exploit and post-compromise operations and include many features for evading defenses. Some adversaries are known to use PowerShell.93
Security Software DiscoveryDiscoveryT1063Adversaries may attempt to get a listing of security software, configurations, defensive tools, and sensors that are installed on the system. This may include things such as local firewall rules, anti-virus, and virtualization. These checks may be built into early-stage remote access tools.

### Windows

Example commands that can be used to obtain security software information are netsh, reg query with Reg, dir with cmd, and Tasklist, but other indicators of discovery behavior may be more specific to the type of software or security system the adversary is looking for.

### Mac

It's becoming more common to see macOS malware perform checks for LittleSnitch and KnockKnock software.
Securityd MemoryCredential AccessT1167In OS X prior to El Capitan, users with root access can read plaintext keychain passwords of logged-in users because Apple’s keychain implementation allows these credentials to be cached so that users are not repeatedly prompted for passwords.942 Apple’s securityd utility takes the user’s logon password, encrypts it with PBKDF2, and stores this master key in memory. Apple also uses a set of keys and algorithms to encrypt the user’s password, but once the master key is found, an attacker need only iterate over the other values to unlock the final password.94 If an adversary can obtain root access (allowing them to read securityd’s memory), then they can scan through memory to find the correct sequence of keys in relatively few tries to decrypt the user’s logon keychain. This provides the adversary with all the plaintext passwords for users, WiFi, mail, browsers, certificates, secure notes, etc.9445
Setuid and SetgidPrivilege EscalationT1166When the setuid or setgid bits are set on Linux or macOS for an application, this means that the application will run with the privileges of the owning user or group respectively. Normally an application is run in the current user’s context, regardless of which user or group owns the application. There are instances where programs need to be executed in an elevated context to function properly, but the user running them doesn’t need the elevated privileges. Instead of creating an entry in the sudoers file, which must be done by root, any user can specify the setuid or setgid flag to be set for their own applications. These bits are indicated with an "s" instead of an "x" when viewing a file's attributes via ls -l. The chmod program can set these bits with via bitmasking, chmod 4777 [file] or via shorthand naming, chmod u+s [file]. An adversary can take advantage of this to either do a shell escape or exploit a vulnerability in an application with the setsuid or setgid bits to get code running in a different user’s context.
SourceExecutionT1153The source command loads functions into the current shell or executes files in the current context. This built-in command can be run in two different ways source /path/to/filename [arguments] or . /path/to/filename [arguments]. Take note of the space after the ".". Without a space, a new shell is created that runs the program instead of running the program within the current context. This is often used to make certain features or functions available to a shell or to update a specific shell's environment. Adversaries can abuse this functionality to execute programs. The file executed with this technique does not need to be marked executable beforehand.
Space after FilenameDefense Evasion
Execution
T1151Adversaries can hide a program's true filetype by changing the extension of a file. With certain file types (specifically this does not work with .app extensions), appending a space to the end of a filename will change how the file is processed by the operating system. For example, if there is a Mach-O executable file called evil.bin, when it is double clicked by a user, it will launch Terminal.app and execute. If this file is renamed to evil.txt, then when double clicked by a user, it will launch with the default text editing application (not executing the binary). However, if the file is renamed to "evil.txt " (note the space at the end), then when double clicked by a user, the true file type is determined by the OS and handled appropriately and the binary will be executed95. Adversaries can use this feature to trick users into double clicking benign-looking files of any format and ultimately executing something malicious.
Standard Application Layer ProtocolCommand and ControlT1071Adversaries may communicate using a common, standardized application layer protocol such as HTTP, HTTPS, SMTP, or DNS to avoid detection by blending in with existing traffic. Commands to the remote system, and often the results of those commands, will be embedded within the protocol traffic between the client and server. For connections that occur internally within an enclave (such as those between a proxy or pivot node and other nodes), commonly used protocols are RPC, SSH, or RDP.
Standard Cryptographic ProtocolCommand and ControlT1032Adversaries use command and control over an encrypted channel using a known encryption protocol like HTTPS or SSL/TLS. The use of strong encryption makes it difficult for defenders to detect signatures within adversary command and control traffic. Some adversaries may use other encryption protocols and algorithms with symmetric keys, such as RC4, that rely on encryption keys encoded into malware configuration files and not public key cryptography. Such keys may be obtained through malware reverse engineering.
Standard Non-Application Layer ProtocolCommand and ControlT1095Use of a standard non-application layer protocol for communication between host and C2 server or among infected hosts within a network. The list of possible protocols is extensive.96 Specific examples include use of network layer protocols, such as the Internet Control Message Protocol (ICMP), and transport layer protocols, such as the User Datagram Protocol (UDP). ICMP communication between hosts is one example. Because ICMP is part of the Internet Protocol Suite, it is required to be implemented by all IP-compatible hosts;97 however, it is not as commonly monitored as other Internet Protocols such as TCP or UDP and may be used by adversaries to hide communications.
Startup ItemsPersistence
Privilege Escalation
T1165Per Apple’s documentation, startup items execute during the final phase of the boot process and contain shell scripts or other executable files along with configuration information used by the system to determine the execution order for all startup items80. This is technically a deprecated version (superseded by Launch Daemons), and thus the appropriate folder, /Library/StartupItems isn’t guaranteed to exist on the system by default, but does appear to exist by default on macOS Sierra. A startup item is a directory whose executable and configuration property list (plist), StartupParameters.plist, reside in the top-level directory. An adversary can create the appropriate folders/files in the StartupItems directory to register their own persistence mechanism34. Additionally, since StartupItems run during the bootup phase of macOS, they will run as root. If an adversary is able to modify an existing Startup Item, then they will be able to Privilege Escalate as well.
SudoPrivilege EscalationT1169The sudoers file, /etc/sudoers, describes which users can run which commands and from which terminals. This also describes which commands users can run as other users or groups. This provides the idea of least privilege such that users are running in their lowest possible permissions for most of the time and only elevate to other users or permissions as needed, typically by prompting for a password. However, the sudoers file can also specify when to not prompt users for passwords with a line like user1 ALL=(ALL) NOPASSWD: ALL50. Adversaries can take advantage of these configurations to execute commands as other users or spawn processes with higher privileges. You must have elevated privileges to edit this file though.
System Information DiscoveryDiscoveryT1082An adversary may attempt to get detailed information about the operating system and hardware, including version, patches, hotfixes, service packs, and architecture.

### Windows

Example commands and utilities that obtain this information include ver, Systeminfo, and dir within cmd for identifying information based on present files and directories.

### Mac

On Mac, the systemsetup command gives a detailed breakdown of the system, but it requires administrative privileges. Additionally, the system_profiler gives a very detailed breakdown of configurations, firewall rules, mounted volumes, hardware, and many other things without needing elevated permissions.
System Network Configuration DiscoveryDiscoveryT1016Adversaries will likely look for details about the network configuration and settings of systems they access or through information discovery of remote systems. Several operating system administration utilities exist that can be used to gather this information. Examples include Arp, ipconfig/ifconfig, nbtstat, and route.
System Network Connections DiscoveryDiscoveryT1049Adversaries may attempt to get a listing of network connections to or from the compromised system they are currently accessing or from remote systems by querying for information over the network.

### Windows

Utilities and commands that acquire this information include netstat, "net use," and "net session" with Net.

### Mac and Linux

In Mac and Linux, netstat and lsof can be used to list current connections. who -a and w can be used to show which users are currently logged in, similar to "net session".
System Owner/User DiscoveryDiscoveryT1033===Windows===

Adversaries may attempt to identify the primary user, currently logged in user, set of users that commonly uses a system, or whether a user is actively using the system. They may do this, for example, by retrieving account usernames or by using Credential Dumping. The information may be collected in a number of different ways using other Discovery techniques, because user and username details are prevalent throughout a system and include running process ownership, file/directory ownership, session information, and system logs.

### Mac

On Mac, the currently logged in user can be identified with users,w, and who.

### Linux

On Linux, the currently logged in user can be identified with w and who.
Third-party SoftwareExecution
Lateral Movement
T1072Third-party applications and software deployment systems may be in use in the network environment for administration purposes (e.g., SCCM, VNC, HBSS, Altiris, etc.). If an adversary gains access to these systems, then they may be able to execute code.

Adversaries may gain access to and use third-party application deployment systems installed within an enterprise network. Access to a network-wide or enterprise-wide software deployment system enables an adversary to have remote code execution on all systems that are connected to such a system. The access may be used to laterally move to systems, gather information, or cause a specific effect, such as wiping the hard drives on all endpoints.

The permissions required for this action vary by system configuration; local credentials may be sufficient with direct access to the deployment server, or specific domain credentials may be required. However, the system may require an administrative account to log in or to perform software deployment.
TrapExecution
Persistence
T1154The trap command allows programs and shells to specify commands that will be executed upon receiving interrupt signals. A common situation is a script allowing for graceful termination and handling of common keyboard interrupts like ctrl+c and ctrl+d. Adversaries can use this to register code to be executed when the shell encounters specific interrupts either to gain execution or as a persistence mechanism. Trap commands are of the following format trap 'command list' signals where "command list" will be executed when "signals" are received.
Two-Factor Authentication InterceptionCredential AccessT1111Use of two- or multifactor authentication is recommended and provides a higher level of security than user names and passwords alone, but organizations should be aware of techniques that could be used to intercept and bypass these security mechanisms. Adversaries may target authentication mechanisms, such as smart cards, to gain access to systems, services, and network resources.

If a smart card is used for two-factor authentication (2FA), then a keylogger will need to be used to obtain the password associated with a smart card during normal use. With both an inserted card and access to the smart card password, an adversary can connect to a network resource using the infected system to proxy the authentication with the inserted hardware token.98

Other methods of 2FA may be intercepted and used by an adversary to authenticate. It is common for one-time codes to be sent via out-of-band communications (email, SMS). If the device and/or service is not secured, then it may be vulnerable to interception. Although primarily focused on by cyber criminals, these authentication mechanisms have been targeted by advanced actors.99

Other hardware tokens, such as RSA SecurID, require the adversary to have access to the physical device or the seed and algorithm in addition to the corresponding credentials.
Uncommonly Used PortCommand and ControlT1065Adversaries may conduct C2 communications over a non-standard port to bypass proxies and firewalls that have been improperly configured.
Valid AccountsDefense Evasion
Persistence
Privilege Escalation
T1078Adversaries may steal the credentials of a specific user or service account using Credential Access techniques. Compromised credentials may be used to bypass access controls placed on various resources on hosts and within the network and may even be used for persistent access to remote systems. Compromised credentials may also grant an adversary increased privilege to specific systems or access to restricted areas of the network. Adversaries may choose not to use malware or tools in conjunction with the legitimate access those credentials provide to make it harder to detect their presence.

Adversaries may also create accounts, sometimes using pre-defined account names and passwords, as a means for persistence through backup access in case other means are unsuccessful.

The overlap of credentials and permissions across a network of systems is of concern because the adversary may be able to pivot across accounts and systems to reach a high level of access (i.e., domain or enterprise administrator) to bypass access controls set within the enterprise.100
Web ServiceCommand and ControlT1102Adversaries may use an existing, legitimate external Web service as a means for relaying commands to a compromised system. Popular websites and social media can act as a mechanism for command and control and give a significant amount of cover due to the likelihood that hosts within a network are already communicating with them prior to a compromise. Using common services, such as those offered by Google or Twitter, makes it easier for adversaries to hide in expected noise. Web service providers commonly use SSL/TLS encryption, giving adversaries an added level of protection.
Web ShellPersistence
Privilege Escalation
T1100A Web shell is a Web script that is placed on an openly accessible Web server to allow an adversary to use the Web server as a gateway into a network. A Web shell may provide a set of functions to execute or a command-line interface on the system that hosts the Web server. In addition to a server-side script, a Web shell may have a client interface program that is used to talk to the Web server (see, for example, China Chopper Web shell client).101 Web shells may serve as Redundant Access or as a persistence mechanism in case an adversary's primary access methods are detected and removed.