Defense Evasion

From enterprise
Jump to: navigation, search

Tactic Description

Defense evasion consists of techniques an adversary may use to evade detection or avoid other defenses. Sometimes these actions are the same as or variations of techniques in other categories that have the added benefit of subverting a particular defense or mitigation. Defense evasion may be considered a set of attributes the adversary applies to all other phases of the operation.

Techniques

Below is a list of all the Defense Evasion techniques in enterprise:

NameTacticsTechnical Description
Access Token ManipulationDefense Evasion
Privilege Escalation
Windows uses access tokens to determine the ownership of a running process. A user can manipulate access tokens to make a running process appear as though it belongs to someone other than the user that started the process. When this occurs, the process also takes on the security context associated with the new token. For example, Microsoft promotes the use of access tokens as a security best practice. Administrators should log in as a standard user but run their tools with administrator privileges using the built-in access token manipulation command runas. Microsoft runas

Adversaries may use access tokens to operate under a different user or system security context to perform actions and evade detection. An adversary can use built-in Windows API functions to copy access tokens from existing processes; this is known as token stealing. An adversary must already be in a privileged user context (i.e. administrator) to steal a token. However, adversaries commonly use token stealing to elevate their security context from the administrator level to the SYSTEM level.Pentestlab Token Manipulation

Adversaries can also create spoofed access tokens if they know the credentials of a user. Any standard user can use the runas command, and the Windows API functions, to do this; it does not require access to an administrator account.

Lastly, an adversary can use a spoofed token to authenticate to a remote system as the account for that token if the account has appropriate permissions on the remote system.

Metasploit’s Meterpreter payload allows arbitrary token stealing and uses token stealing to escalate privileges. Metasploit access token The Cobalt Strike beacon payload allows arbitrary token stealing and can also create tokens. Cobalt Strike Access Token
Binary PaddingDefense EvasionSome 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.
Bypass User Account ControlDefense Evasion
Privilege Escalation
Windows User Account Control (UAC) allows a program to elevate its privileges to perform a task under administrator-level permissions by prompting the user for confirmation. The impact to the user ranges from denying the operation under high enforcement to allowing the user to perform the action if they are in the local administrators group and click through the prompt or allowing them to enter an administrator password to complete the action.TechNet How UAC Works

If the UAC protection level of a computer is set to anything but the highest level, certain Windows programs are allowed to elevate privileges or execute some elevated COM objects without prompting the user through the UAC notification box.TechNet Inside UACMSDN COM Elevation An example of this is use of rundll32.exe to load a specifically crafted DLL which loads an auto-elevated COM object and performs a file operation in a protected directory which would typically require elevated access. Malicious software may also be injected into a trusted process to gain elevated privileges without prompting a user.Davidson Windows Adversaries can use these techniques to elevate privileges to administrator if the target process is unprotected.

Many methods have been discovered to bypass UAC. The Github readme page for UACMe contains an extensive list of methodsGithub UACMe that have been discovered and implemented within UACMe, but may not be a comprehensive list of bypasses. Additional bypass methods are regularly discovered and some used in the wild, such as:

  • eventvwr.exe can auto-elevate and execute a specified binary or script.enigma0x3 Fileless UAC BypassFortinet Fareit
Another bypass is possible through some Lateral Movement techniques if credentials for an account with administrator privileges are known, since UAC is a single system security mechanism, and the privilege or integrity of a process running on one system will be unknown on lateral systems and default to high integrity.SANS UAC Bypass
Clear Command HistoryDefense EvasionmacOS 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.
Code SigningDefense EvasionCode signing provides a level of authenticity on a binary from the developer and a guarantee that the binary has not been tampered with.Wikipedia Code Signing However, adversaries are known to use code signing certificates to masquerade malware and tools as legitimate binariesJanicab. The certificates used during an operation may be created, forged, or stolen by the adversary.Securelist Digital CertificatesSymantec Digital Certificates

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.Wikipedia Code Signing

Code signing certificates may be used to bypass security policies that require signed code to execute on a system.
Component FirmwareDefense Evasion
Persistence
Some adversaries may employ sophisticated means to compromise computer components and install malicious firmware that will execute adversary code outside of the operating system and main system firmware or BIOS. This technique may be similar to System Firmware but conducted upon other system components that may not have the same capability or level of integrity checking. Malicious device firmware could provide both a persistent level of access to systems despite potential typical failures to maintain access and hard disk re-images, as well as a way to evade host software-based defenses and integrity checks.
Component Object Model HijackingDefense Evasion
Persistence
The Microsoft Component Object Model (COM) is a system within Windows to enable interaction between software components through the operating system.Microsoft Component Object Model Adversaries can use this system to insert malicious code that can be executed in place of legitimate software through hijacking the COM references and relationships as a means for persistence. Hijacking a COM object requires a change in the Windows Registry to replace a reference to a legitimate system component which may cause that component to not work when executed. When that system component is executed through normal system operation the adversary's code will be executed instead.GDATA COM Hijacking An adversary is likely to hijack objects that are used frequently enough to maintain a consistent level of persistence, but are unlikely to break noticeable functionality within the system as to avoid system instability that could lead to detection.
DLL InjectionDefense Evasion
Privilege Escalation
DLL injection is used to run code in the context of another process by causing the other process to load and execute code. Running code in the context of another process provides adversaries many benefits, such as access to the process's memory and permissions. It also allows adversaries to mask their actions under a legitimate process. A more sophisticated kind of DLL injection, reflective DLL injection, loads code without calling the normal Windows API calls, potentially bypassing DLL load monitoring. Numerous methods of DLL injection exist on Windows, including modifying the Registry, creating remote threads, Windows hooking APIs, and DLL pre-loading.CodeProject Inject CodeWikipedia DLL Injection
DLL Search Order HijackingDefense Evasion
Persistence
Privilege Escalation
Windows systems use a common method to look for required DLLs to load into a program.Microsoft DLL Search Adversaries may take advantage of the Windows DLL search order and programs that ambiguously specify DLLs to gain privilege escalation and persistence.

Adversaries may perform DLL preloading, also called binary planting attacks,OWASP Binary Planting by placing a malicious DLL with the same name as an ambiguously specified DLL in a location that Windows searches before the legitimate DLL. Often this location is the current working directory of the program. Remote DLL preloading attacks occur when a program sets its current directory to a remote location such as a Web share before loading a DLL.Microsoft 2269637 Adversaries may use this behavior to cause the program to load a malicious DLL.

Adversaries may also directly modify the way a program loads DLLs by replacing an existing DLL or modifying a .manifest or .local redirection file, directory, or junction to cause the program to load a different DLL to maintain persistence or privilege escalation.Microsoft DLL RedirectionMicrosoft ManifestsMandiant Search Order

If a search order-vulnerable program is configured to run at a higher privilege level, then the adversary-controlled DLL that is loaded will also be executed at the higher level. In this case, the technique could be used for privilege escalation from user to administrator or SYSTEM or from administrator to SYSTEM, depending on the program.

Programs that fall victim to path hijacking may appear to behave normally because malicious DLLs may be configured to also load the legitimate DLLs they were meant to replace.
DLL Side-LoadingDefense EvasionPrograms may specify DLLs that are loaded at runtime. Programs that improperly or vaguely specify a required DLL may be open to a vulnerability in which an unintended DLL is loaded. Side-loading vulnerabilities specifically occur when Windows Side-by-Side (WinSxS) manifestsMSDN Manifests are not explicit enough about characteristics of the DLL to be loaded. Adversaries may take advantage of a legitimate program that is vulnerable to side-loading to load a malicious DLL.Stewart 2014 Adversaries likely use this technique as a means of masking actions they perform under a legitimate, trusted system or software process.
Deobfuscate/Decode Files or InformationDefense EvasionAdversaries may use Obfuscated Files or Information to hide artifacts of an intrusion from analysis. They may require separate mechanisms to decode or deobfuscate that information depending on how they intend to use it. Methods for doing that include built-in functionality of malware, Scripting, PowerShell, or by using utilities present on the system. One such example is use of certutil to decode a remote access tool portable executable file that has been hidden inside a certificate file.Malwarebytes Targeted Attack against Saudi Arabia
Disabling Security ToolsDefense EvasionAdversaries 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.
Exploitation of VulnerabilityCredential Access
Defense Evasion
Lateral Movement
Privilege Escalation
Exploitation 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.Technet MS14-068ADSecurity Detecting Forged Tickets
File DeletionDefense EvasionMalware, 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.Trend Micro APT Attack Tools
File System Logical OffsetsDefense EvasionWindows allows programs to have direct access to logical volumes. Programs with direct access may read and write files directly from the drive by analyzing file system data structures. This technique bypasses Windows file access controls as well as file system monitoring tools.Hakobyan 2009 Utilities, such as NinjaCopy, exist to perform these actions in PowerShell.Github PowerSploit Ninjacopy
Gatekeeper BypassDefense EvasionIn 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 checkMethods of Mac Malware Persistence. 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 Clearing quarantine attributeOceanLotus for OS X.

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 Bypassing Gatekeeper.
HISTCONTROLDefense EvasionThe 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
To 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 Sofacy Komplex TrojanAntiquated Mac Malware. 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.appWireLurker. 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 EvasionEvery 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 401Cybereason OSX Pirrit.
Hidden WindowDefense EvasionThe 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 Antiquated Mac Malware.
Indicator BlockingDefense EvasionAn adversary may attempt to block indicators or events from leaving the host machine. In the case of network-based reporting of indicators, an adversary may block traffic associated with reporting to prevent central analysis. This may be accomplished by many means, such as stopping a local process or creating a host-based firewall rule to block traffic to a specific server.
Indicator Removal from ToolsDefense EvasionIf 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 EvasionAdversaries 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.
Install Root CertificateDefense EvasionRoot certificates are used in public key cryptography to identify a root certificate authority (CA). When a root certificate is installed, the system or application will trust certificates in the root's chain of trust that have been signed by the root certificate.Wikipedia Root Certificate Certificates are commonly used for establishing secure TLS/SSL communications within a web browser. When a user attempts to browse a website that presents a certificate that is not trusted an error message will be displayed to warn the user of the security risk. Depending on the security settings, the browser may not allow the user to establish a connection to the website.

Installation of a root certificate on a compromised system would give an adversary a way to degrade the security of that system. Adversaries have used this technique to avoid security warnings prompting users when compromised systems connect over HTTPS to adversary controlled web servers that spoof legitimate websites in order to collect login credentials.Operation Emmental

Atypical root certificates have also been pre-installed on systems by the manufacturer or in the software supply chain and were used in conjunction with malware/adware to provide a man-in-the-middle capability for intercepting information transmitted over secure TLS/SSL communications.Kaspersky Superfish
InstallUtilDefense Evasion
Execution
InstallUtil is a command-line utility that allows for installation and uninstallation of resources by executing specific installer components specified in .NET binaries.MSDN InstallUtil InstallUtil is located in the .NET directory on a Windows system: C:\Windows\Microsoft.NET\Framework\v<version>\InstallUtil.exe.InstallUtil.exe is digitally signed by Microsoft. Adversaries may use InstallUtil to proxy execution of code through a trusted Windows utility. InstallUtil may also be used to bypass process whitelisting through use of attributes within the binary that execute the class decorated with the attribute [System.ComponentModel.RunInstaller(true)].SubTee GitHub All The Things Application Whitelisting Bypass
LC_MAIN HijackingDefense EvasionAs 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 Prolific OSX Malware History. 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 Methods of Mac Malware Persistence. By modifying a binary in this way, application whitelisting can be bypassed because the file name or application path is still the same.
LaunchctlDefense Evasion
Execution
Persistence
Launchctl 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 Sofacy Komplex Trojan. 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.
MasqueradingDefense EvasionMasquerading occurs when an executable, legitimate or malicious, is placed in a commonly trusted location (such as C:\Windows\System32) or named with a common name (such as "explorer.exe" or "svchost.exe") to bypass tools that trust executables by relying on file name or path. An adversary may even use a renamed copy of a legitimate utility, such as rundll32.exe.Endgame Masquerade Ball Masquerading also may be done to deceive defenders and system administrators into thinking a file is benign by associating the name with something that is thought to be legitimate.
Modify RegistryDefense EvasionAdversaries may interact with the Windows Registry to hide configuration information within Registry keys, remove information as part of cleaning up, or as part of other techniques to aid in Persistence and Execution.

Access to specific areas of the Registry depends on account permissions, some requiring administrator-level access. The built-in Windows command-line utility Reg may be used for local or remote Registry modification.Microsoft Reg Other tools may also be used, such as a remote access tool, which may contain functionality to interact with the Registry through the Windows API (see examples).

The Registry of a remote system may be modified to aid in execution of files as part of Lateral Movement. It requires the remote Registry service to be running on the target system.Microsoft Remote Often Valid Accounts are required, along with access to the remote system's Windows Admin Shares for RPC communication.
NTFS Extended AttributesDefense EvasionData or executables may be stored in New Technology File System (NTFS) partition metadata instead of directly in files. This may be done to evade some defenses, such as static indicator scanning tools and anti-virus.Journey into IR ZeroAccess NTFS EA The NTFS format has a feature called Extended Attributes (EA), which allows data to be stored as an attribute of a file or folder.Microsoft File Streams
Network Share Connection RemovalDefense EvasionWindows shared drive and Windows Admin Shares connections can be removed when no longer needed. Net is an example utility that can be used to remove network share connections with the net use \\system\share /delete command.Technet Net Use Adversaries may remove share connections that are no longer useful in order to clean up traces of their operation.
Obfuscated Files or InformationDefense EvasionAdversaries may attempt to make an executable or file difficult to discover or analyze by encrypting, encoding, or otherwise obfuscating its contents on the system.
Plist ModificationDefense Evasion
Persistence
Privilege Escalation
Property 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 mechanismSofacy Komplex Trojan.
Process HollowingDefense Evasion
Execution
Process hollowing occurs when a process is created in a suspended state and the process's memory is replaced with the code of a second program so that the second program runs instead of the original program. Windows and process monitoring tools believe the original process is running, whereas the actual program running is different.Leitch Hollowing Process hollowing may be used similarly to DLL Injection to evade defenses and detection analysis of malicious process execution by launching adversary-controlled code under the context of a legitimate process.
Redundant AccessDefense Evasion
Persistence
Adversaries may use more than one remote access tool with varying command and control protocols as a hedge against detection. If one type of tool is detected and blocked or removed as a response but the organization did not gain a full understanding of the adversary's tools and access, then the adversary will be able to retain access to the network. Adversaries may also attempt to gain access to Valid Accounts to use External Remote Services such as external VPNs as a way to maintain access despite interruptions to remote access tools deployed within a target network.Mandiant APT1 Use of a Web Shell is one such way to maintain access to a network through an externally accessible Web server.
Regsvcs/RegasmDefense Evasion
Execution
Regsvcs and Regasm are Windows command-line utilities that are used to register .NET Component Object Model (COM) assemblies. Both are digitally signed by Microsoft.MSDN RegsvcsMSDN Regasm Adversaries can use Regsvcs and Regasm to proxy execution of code through a trusted Windows utility. Both utilities may be used to bypass process whitelisting through use of attributes within the binary to specify code that should be run before registration or unregistration: [ComRegisterFunction] or [ComUnregisterFunction] respectively. The code with the registration and unregistration attributes will be executed even if the process is run under insufficient privileges and fails to execute.SubTee GitHub All The Things Application Whitelisting Bypass
Regsvr32Defense Evasion
Execution
Regsvr32.exe is a command-line program used to register and unregister object linking and embedding controls, including dynamic link libraries (DLLs), on Windows systems. Regsvr32.exe can be used to execute arbitrary binaries.Microsoft Regsvr32

Adversaries may take advantage of this functionality to proxy execution of code to avoid triggering security tools that may not monitor execution of, and modules loaded by, the regsvr32.exe process because of whitelists or false positives from Windows using regsvr32.exe for normal operations. Regsvr32.exe is also a Microsoft signed binary.

Regsvr32.exe can also be used to specifically bypass process whitelisting using functionality to load COM scriptlets to execute DLLs under user permissions. Since regsvr32.exe is network and proxy aware, the scripts can be loaded by passing a uniform resource locator (URL) to file on an external Web server as an argument during invocation. This method makes no changes to the Registry as the COM object is not actually registered, only executed.SubTee Regsvr32 Whitelisting Bypass This variation of the technique has been used in campaigns targeting governments.FireEye Regsvr32 Targeting Mongolian Gov
RootkitDefense EvasionRootkits are programs that hide the existence of malware by intercepting and modifying operating system API calls that supply system information. 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.Wikipedia Rootkit Adversaries may use rootkits to hide the presence of programs, files, network connections, services, drivers, and other system components.
Rundll32Defense Evasion
Execution
The rundll32.exe program can be called to execute an arbitrary binary. Adversaries may take advantage of this functionality to proxy execution of code to avoid triggering security tools that may not monitor execution of the rundll32.exe process because of whitelists or false positives from Windows using rundll32.exe for normal operations.
ScriptingDefense Evasion
Execution
Adversaries 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. MetasploitMetasploit, VeilVeil, and PowerSploitPowersploit 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.Alperovitch 2014
Software PackingDefense EvasionSoftware packing is a method of compressing or encrypting an executable. Packing an executable changes the file signature in an attempt to avoid signature-based detection. Most decompression techniques decompress the executable code in memory. Utilities used to perform software packing are called packers. Example packers are MPRESS and UPX. A more comprehensive list of known packers is available,Wikipedia Exe Compression but adversaries may create their own packing techniques that do not leave the same artifacts as well-known packers to evade defenses.
Space after FilenameDefense Evasion
Execution
Adversaries 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 executedMac Backdoors are back. Adversaries can use this feature to trick users into double clicking benign-looking files of any format and ultimately executing something malicious.
TimestompDefense EvasionTimestomping is a technique that modifies the timestamps of a file (the modify, access, create, and change times), often to mimic files that are in the same folder. This is done, for example, on files that have been modified or created by the adversary so that they do not appear conspicuous to forensic investigators or file analysis tools. Timestomping may be used along with file name Masquerading to hide malware and tools.WindowsIR Anti-Forensic Techniques
Trusted Developer UtilitiesDefense Evasion
Execution
There are many utilities used for software development related tasks that can be used to execute code in various forms to assist in development, debugging, and reverse engineering. These utilities may often be signed with legitimate certificates that allow them to execute on a system and proxy execution of malicious code through a trusted process that effectively bypasses application whitelisting defensive solutions.

MSBuild

MSBuild.exe (Microsoft Build Engine) is a software build platform used by Visual Studio. It takes XML formatted project files that define requirements for building various platforms and configurations.MSDN MSBuild

Adversaries can use MSBuild to proxy execution of code through a trusted Windows utility. The inline task capability of MSBuild that was introduced in .NET version 4 allows for C# code to be inserted into the XML project file.MSDN MSBuild Inline Tasks MSBuild will compile and execute the inline task. MSBuild.exe is a signed Microsoft binary, so when it is used this way it can execute arbitrary code and bypass application whitelisting defenses that are configured to allow MSBuild.exe execution.SubTee GitHub All The Things Application Whitelisting Bypass

DNX

The .NET Execution Environment (DNX), dnx.exe, is a software development kit packaged with Visual Studio Enterprise. It was retired in favor of .NET Core CLI in 2016.Microsoft Migrating from DNX DNX is not present on standard builds of Windows and may only be present on developer workstations using older versions of .NET Core and ASP.NET Core 1.0. The dnx.exe executable is signed by Microsoft.

An adversary can use dnx.exe to proxy execution of arbitrary code to bypass application whitelist policies that do not account for DNX.engima0x3 DNX Bypass

RCSI

The rcsi.exe utility is a non-interactive command-line interface for C# that is similar to csi.exe. It was provided within an early version of the Roslyn .NET Compiler Platform but has since been deprecated for an integrated solution.Microsoft Roslyn CPT RCSI The rcsi.exe binary is signed by Microsoft.engima0x3 RCSI Bypass

C# .csx script files can be written and executed with rcsi.exe at the command-line. An adversary can use rcsi.exe to proxy execution of arbitrary code to bypass application whitelisting policies that do not account for execution of rcsi.exe.engima0x3 RCSI Bypass

WinDbg/CDB

WinDbg is a Microsoft Windows kernel and user-mode debugging utility. The Microsoft Console Debugger (CDB) cdb.exe is also user-mode debugger. Both utilities are included in Windows software development kits and can be used as standalone tools.Microsoft Debugging Tools for Windows They are commonly used in software development and reverse engineering and may not be found on typical Windows systems. Both WinDbg.exe and cdb.exe binaries are signed by Microsoft.

An adversary can use WinDbg.exe and cdb.exe to proxy execution of arbitrary code to bypass application whitelist policies that do not account for execution of those utilities.Exploit Monday WinDbg

It is likely possible to use other debuggers for similar purposes, such as the kernel-mode debugger kd.exe, which is also signed by Microsoft.
Valid AccountsDefense Evasion
Persistence
Privilege Escalation
Adversaries 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.TechNet Credential Theft