T1556.001: Domain Controller Authentication

Adversaries may patch the authentication process on a domain controller to bypass the typical authentication mechanisms and enable access to accounts.

Malware may be used to inject false credentials into the authentication process on a domain controller with the intent of creating a backdoor used to access any user’s account and/or credentials (ex: Skeleton Key). Skeleton key works through a patch on an enterprise domain controller authentication process (LSASS) with credentials that adversaries may use to bypass the standard authentication system. Once patched, an adversary can use the injected password to successfully authenticate as any domain user account (until the the skeleton key is erased from memory by a reboot of the domain controller). Authenticated access may enable unfettered access to hosts and/or resources within single-factor authentication environments.

Positive Technologies products that cover the technique

MaxPatrol SIEM knowledge base

active_directory_attacks: PT-CR-834: Enable_SAN_Flag_CA_Policy: The EDITF_ATTRIBUTESUBJECTALTNAME2 flag, which allows any user to add the Subject Alternative Name attribute to the certificate signing request, is installed on the certificate server. Using this flag may allow attackers to authenticate on behalf of another user, including the domain administrator

Detection

IDDS0009Data source and componentProcess: OS API ExecutionDescription

Monitor for API calls to OpenProcess that can be used to manipulate lsass.exe running on a domain controller

IDDS0009Data source and componentProcess: Process AccessDescription

Monitor for unexpected processes interacting with the authentication process on a domain controller to bypass the typical authentication mechanisms and enable access to accounts.

IDDS0022Data source and componentFile: File ModificationDescription

Monitor for changes to functions exported from authentication-related system DLLs (such as cryptdll.dll and samsrv.dll).

IDDS0028Data source and componentLogon Session: Logon Session CreationDescription

Monitor for newly constructed logon behavior across systems that share accounts, either user, admin, or service accounts. Examples: one account logged into multiple systems simultaneously; multiple accounts logged into the same machine simultaneously; accounts logged in at odd times (ex: when the user is not present) or outside of business hours. Activity may be from interactive login sessions or process ownership from accounts being used to execute binaries on a remote system as a particular account. Correlate other security systems with login information (e.g., a user has an active login session but has not entered the building or does not have VPN access). Configure robust, consistent account activity audit policies across the enterprise and with externally accessible services.

Mitigation

IDM1032NameMulti-factor AuthenticationDescription

Integrating multi-factor authentication (MFA) as part of organizational policy can greatly reduce the risk of an adversary gaining control of valid credentials that may be used for additional tactics such as initial access, lateral movement, and collecting information. MFA can also be used to restrict access to cloud resources and APIs.

IDM1026NamePrivileged Account ManagementDescription

Audit domain and local accounts as well as their permission levels routinely to look for situations that could allow an adversary to gain wide access by obtaining credentials of a privileged account. These audits should also include if default accounts have been enabled, or if new local accounts are created that have not be authorized. Follow best practices for design and administration of an enterprise network to limit privileged account use across administrative tiers.

IDM1025NamePrivileged Process IntegrityDescription

Enabled features, such as Protected Process Light (PPL), for LSA.