Credential Access

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Tactic Description

Credential access represents techniques resulting in access to or control over system, domain, or service credentials that are used within an enterprise environment. Adversaries will likely attempt to obtain legitimate credentials from users or administrator accounts (local system administrator or domain users with administrator access) to use within the network. This allows the adversary to assume the identity of the account, with all of that account's permissions on the system and network, and makes it harder for defenders to detect the adversary. With sufficient access within a network, an adversary can create accounts for later use within the environment.

Techniques

Below is a list of all the Credential Access techniques in enterprise:

NameTacticsTechnical Description
Account ManipulationCredential AccessAccount manipulation may aid adversaries in maintaining access to credentials and certain permission levels within an environment. Manipulation could consist of modifying permissions, modifying credentials, adding or changing permission groups, modifying account settings, or modifying how authentication is performed. In order to create or manipulate accounts, the adversary must already have sufficient permissions on systems or the domain.
Bash HistoryCredential AccessBash 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.1
Brute ForceCredential AccessAdversaries may use brute force techniques to attempt access to accounts when passwords are unknown or when password hashes are obtained.

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.2

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.3

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.4
Credential DumpingCredential AccessCredential dumping is the process of obtaining account login and password information, normally in the form of a hash or a clear text password, from the operating system and software. Credentials can then be used to perform Lateral Movement and access restricted information.

Several of the tools mentioned in this technique may be used by both adversaries and professional security testers. Additional custom tools likely exist as well.

SAM (Security Accounts Manager)

The SAM is a database file that contains local accounts for the host, typically those found with the ‘net user’ command. To enumerate the SAM database, system level access is required.   A number of tools can be used to retrieve the SAM file through in-memory techniques:

Alternatively, the SAM can be extracted from the Registry with Reg:

  • reg save HKLM\sam sam
  • reg save HKLM\system system

Creddump7 can then be used to process the SAM database locally to retrieve hashes.5

Notes: Rid 500 account is the local, in-built administrator. Rid 501 is the guest account. User accounts start with a RID of 1,000+.

Cached Credentials

The DCC2 (Domain Cached Credentials version 2) hash, used by Windows Vista and newer caches credentials when the domain controller is unavailable. The number of default cached credentials varies, and this number can be altered per system. This hash does not allow pass-the-hash style attacks.   A number of tools can be used to retrieve the SAM file through in-memory techniques.

Alternatively, reg.exe can be used to extract from the Registry and Creddump7 used to gather the credentials.

Notes: Cached credentials for Windows Vista are derived using PBKDF2.

Local Security Authority (LSA) Secrets

With SYSTEM access to a host, the LSA secrets often allows trivial access from a local account to domain-based account credentials. The Registry is used to store the LSA secrets.   When services are run under the context of local or domain users, their passwords are stored in the Registry. If auto-logon is enabled, this information will be stored in the Registry as well.   A number of tools can be used to retrieve the SAM file through in-memory techniques.

Alternatively, reg.exe can be used to extract from the Registry and Creddump7 used to gather the credentials.

Notes: The passwords extracted by his mechanism are UTF-16 encoded, which means that they are returned in plaintext. Windows 10 adds protections for LSA Secrets described in Mitigation.

NTDS from Domain Controller

Active Directory stores information about members of the domain including devices and users to verify credentials and define access rights. The Active Directory domain database is stored in the NTDS.dit file. By default the NTDS file will be located in %SystemRoot%\NTDS\Ntds.dit of a domain controller.6

The following tools and techniques can be used to enumerate the NTDS file and the contents of the entire Active Directory hashes.  

  • Volume Shadow Copy
  • secretsdump.py
  • Using the in-built Windows tool, ntdsutil.exe
  • Invoke-NinjaCopy

Group Policy Preference (GPP) Files

Group Policy Preferences (GPP) are tools that allowed administrators to create domain policies with embedded credentials. These policies, amongst other things, allow administrators to set local accounts.   These group policies are stored in SYSVOL on a domain controller, this means that any domain user can view the SYSVOL share and decrypt the password (the AES private key was leaked on-line.78   The following tools and scripts can be used to gather and decrypt the password file from Group Policy Preference XML files:  

  • Metasploit’s post exploitation module: "post/windows/gather/credentials/gpp"
  • Get-GPPPassword9
  • gpprefdecrypt.py

  Notes: On the SYSVOL share, the following can be used to enumerate potential XML files. dir /s *.xml

Service Principal Names (SPNs)

See Kerberoasting.

Plaintext Credentials

After a user logs on to a system, a variety of credentials are generated and stored in the Local Security Authority Subsystem Service (LSASS) process in memory. These credentials can be harvested by a administrative user or SYSTEM.   SSPI (Security Support Provider Interface) functions as a common interface to several Security Support Providers (SSPs): A Security Support Provider is a dynamic-link library (DLL) that makes one or more security packages available to applications.

The following SSPs can be used to access credentials:   Msv: Interactive logons, batch logons, and service logons are done through the MSV authentication package. Wdigest: The Digest Authentication protocol is designed for use with Hypertext Transfer Protocol (HTTP) and Simple Authentication Security Layer (SASL) exchanges.10 Kerberos: Preferred for mutual client-server domain authentication in Windows 2000 and later. CredSSP:  Provides SSO and Network Level Authentication for Remote Desktop Services.11   The following tools can be used to enumerate credentials:  

  As well as in-memory techniques, the LSASS process memory can be dumped from the target host and analyzed on a local system.   For example, on the target host use procdump:

  • procdump -ma lsass.exe lsass_dump

  Locally, mimikatz can be run:

  • sekurlsa::Minidump lsassdump.dmp
  • sekurlsa::logonPasswords

DCSync

DCSync is a variation on credential dumping which can be used to acquire sensitive information from a domain controller. Rather than executing recognizable malicious code, the action works by abusing the domain controller's application programming interface (API)12131415 to simulate the replication process from a remote domain controller. Any members of the Administrators, Domain Admins, Enterprise Admin groups or computer accounts on the domain controller are able to run DCSync to pull password data 16 from Active Directory, which may include current and historical hashes of potentially useful accounts such as KRBTGT and Administrators. The hashes can then in turn be used to create a Golden Ticket for use in Pass the Ticket17 or change an account's password as noted in Account Manipulation.18 DCSync functionality has been included in the "lsadump" module in Mimikatz.19 Lsadump also includes NetSync, which performs DCSync over a legacy replication protocol.20
Credentials in FilesCredential AccessAdversaries 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.21 Passwords may also be obtained from Group Policy Preferences stored on the Windows Domain Controller.8
Credentials in RegistryCredential AccessThe Windows Registry stores configuration information that can be used by the system or other programs. Adversaries may query the Registry looking for credentials and passwords that have been stored for use by other programs or services. Sometimes these credentials are used for automatic logons.

Example commands to find Registry keys related to password information:22

  • Local Machine Hive: reg query HKLM /f password /t REG_SZ /s
  • Current User Hive: reg query HKCU /f password /t REG_SZ /s
Exploitation for Credential AccessCredential AccessExploitation 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. Credentialing and authentication mechanisms may be targeted for exploitation by adversaries as a means to gain access to useful credentials or circumvent the process to gain access to systems. One example of this is MS14-068, which targets Kerberos and can be used to forge Kerberos tickets using domain user permissions.2324 Exploitation for credential access may also result in Privilege Escalation depending on the process targeted or credentials obtained.
Forced AuthenticationCredential AccessThe Server Message Block (SMB) protocol is commonly used in Windows networks for authentication and communication between systems for access to resources and file sharing. When a Windows system attempts to connect to an SMB resource it will automatically attempt to authenticate and send credential information for the current user to the remote system. 25 This behavior is typical in enterprise environments so that users do not need to enter credentials to access network resources. Web Distributed Authoring and Versioning (WebDAV) is typically used by Windows systems as a backup protocol when SMB is blocked or fails. WebDAV is an extension of HTTP and will typically operate over TCP ports 80 and 443.2627

Adversaries may take advantage of this behavior to gain access to user account hashes through forced SMB authentication. An adversary can send an attachment to a user through spearphishing that contains a resource link to an external server controlled by the adversary, or place a specially crafted file on navigation path for privileged accounts (e.g. .SCF file placed on desktop) or on a publicly accessible share to be accessed by victim(s). When the user's system accesses the untrusted resource it will attempt authentication and send information including the user's hashed credentials over SMB to the adversary controlled server.28 With access to the credential hash, an adversary can perform off-line Brute Force cracking to gain access to plaintext credentials, or reuse it for Pass the Hash.29

There are several different ways this can occur.30 Some specifics from in-the-wild use include:

  • A spearphishing attachment containing a document with a resource that is automatically loaded when the document is opened. The document can include, for example, a request similar to file[:]//[remote address]/Normal.dotm to trigger the SMB request.31
  • A modified .LNK or .SCF file with the icon filename pointing to an external reference such as \\[remote address]\pic.png that will force the system to load the resource when the icon is rendered to repeatedly gather credentials.31
HookingCredential Access
Persistence
Privilege Escalation
Windows processes often leverage application programming interface (API) functions to perform tasks that require reusable system resources. Windows API functions are typically stored in dynamic-link libraries (DLLs) as exported functions. Hooking involves redirecting calls to these functions and can be implemented via:
  • Hooks procedures, which intercept and execute designated code in response to events such as messages, keystrokes, and mouse inputs.3233
  • Import address table (IAT) hooking, which use modifications to a process’s IAT, where pointers to imported API functions are stored.333435
  • Inline hooking, which overwrites the first bytes in an API function to redirect code flow.333635
  • Similar to Process Injection, adversaries may use hooking to load and execute malicious code within the context of another process, masking the execution while also allowing access to the process's memory and possibly elevated privileges. Installing hooking mechanisms may also provide Persistence via continuous invocation when the functions are called through normal use.

    Malicious hooking mechanisms may also capture API calls that include parameters that reveal user authentication credentials for Credential Access.37

    Hooking is commonly utilized by Rootkits to conceal files,

    processes, Registry keys, and other objects in order to hide malware and associated behaviors.38
    Input CaptureCollection
    Credential Access
    Adversaries 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,39 but other methods exist to target information for specific purposes, such as performing a UAC prompt or wrapping the Windows default credential provider.40

    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.41
    Input PromptCredential AccessWhen 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 "") 42

    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.43
    KerberoastingCredential AccessService principal names (SPNs) are used to uniquely identify each instance of a Windows service. To enable authentication, Kerberos requires that SPNs be associated with at least one service logon account (an account specifically tasked with running a service44).45464748

    Adversaries possessing a valid Kerberos ticket-granting ticket (TGT) may request one or more Kerberos ticket-granting service (TGS) service tickets for any SPN from a domain controller (DC).4950 Portions of these tickets may be encrypted with the RC4 algorithm, meaning the Kerberos 5 TGS-REP etype 23 hash of the service account associated with the SPN is used as the private key and is thus vulnerable to offline Brute Force attacks that may expose plaintext credentials.504948

    This same attack could be executed using service tickets captured from network traffic.50

    Cracked hashes may enable Persistence, Privilege Escalation, and Lateral Movement via access to Valid Accounts.47
    KeychainCredential AccessKeychains 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/.51 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.1 By default, the passphrase for the keychain is the user’s logon credentials.
    LLMNR/NBT-NS PoisoningCredential AccessLink-Local Multicast Name Resolution (LLMNR) and NetBIOS Name Service (NBT-NS) are Microsoft Windows components that serve as alternate methods of host identification. LLMNR is based upon the Domain Name System (DNS) format and allows hosts on the same local link to perform name resolution for other hosts. NBT-NS identifies systems on a local network by their NetBIOS name.5253

    Adversaries can spoof an authoritative source for name resolution on a victim network by responding to LLMNR (UDP 5355)/NBT-NS (UDP 137) traffic as if they know the identity of the requested host, effectively poisoning the service so that the victims will communicate with the adversary controlled system. If the requested host belongs to a resource that requires identification/authentication, the username and NTLMv2 hash will then be sent to the adversary controlled system. The adversary can then collect the hash information sent over the wire through tools that monitor the ports for traffic or through Network Sniffing and crack the hashes offline through Brute Force to obtain the plaintext passwords.

    Several tools exist that can be used to poison name services within local networks such as NBNSpoof, Metasploit, and Responder.545556
    Network SniffingCredential AccessNetwork 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.
    Password Filter DLLCredential AccessWindows password filters are password policy enforcement mechanisms for both domain and local accounts. Filters are implemented as dynamic link libraries (DLLs) containing a method to validate potential passwords against password policies. Filter DLLs can be positioned on local computers for local accounts and/or domain controllers for domain accounts.

    Before registering new passwords in the Security Accounts Manager (SAM), the Local Security Authority (LSA) requests validation from each registered filter. Any potential changes cannot take effect until every registered filter acknowledges validation.

    Adversaries can register malicious password filters to harvest credentials from local computers and/or entire domains. To perform proper validation, filters must receive plain-text credentials from the LSA. A malicious password filter would receive these plain-text credentials every time a password request is made.57
    Private KeysCredential AccessPrivate cryptographic keys and certificates are used for authentication, encryption/decryption, and digital signatures.58

    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.5960
    Securityd MemoryCredential AccessIn 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.611 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.61 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.6142
    Two-Factor Authentication InterceptionCredential AccessUse 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.62

    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.63

    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.

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