Adversaries may modify authentication mechanisms and processes to access user credentials or enable otherwise unwarranted access to accounts. The authentication process is handled by mechanisms, such as the Local Security Authentication Server (LSASS) process and the Security Accounts Manager (SAM) on Windows, pluggable authentication modules (PAM) on Unix-based systems, and authorization plugins on MacOS systems, responsible for gathering, storing, and validating credentials. By modifying an authentication process, an adversary may be able to authenticate to a service or system without using Valid Accounts.
Adversaries may maliciously modify a part of this process to either reveal credentials or bypass authentication mechanisms. Compromised credentials or access may be used to bypass access controls placed on various resources on systems within the network and may even be used for persistent access to remote systems and externally available services, such as VPNs, Outlook Web Access and remote desktop.
Review authentication logs to ensure that mechanisms such as enforcement of MFA are functioning as intended.
Periodically review the hybrid identity solution in use for any discrepancies. For example, review all Pass Through Authentication (PTA) agents in the Azure Management Portal to identify any unwanted or unapproved ones. If ADFS is in use, review DLLs and executable files in the AD FS and Global Assembly Cache directories to ensure that they are signed by Microsoft. Note that in some cases binaries may be catalog-signed, which may cause the file to appear unsigned when viewing file properties.
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.
|M1028||Operating System Configuration||
Ensure only valid password filters are registered. Filter DLLs must be present in Windows installation directory (
|M1026||Privileged Account Management||
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. 
Limit access to the root account and prevent users from modifying protected components through proper privilege separation (ex SELinux, grsecurity, AppArmor, etc.) and limiting Privilege Escalation opportunities.
Limit on-premises accounts with access to the hybrid identity solution in place. For example, limit Azure AD Global Administrator accounts to only those required, and ensure that these are dedicated cloud-only accounts rather than hybrid ones.
|M1025||Privileged Process Integrity||
Enabled features, such as Protected Process Light (PPL), for LSA.
|M1022||Restrict File and Directory Permissions||
Restrict write access to the
|M1018||User Account Management||
Ensure that proper policies are implemented to dictate the the secure enrollment and deactivation of authentication mechanisms, such as MFA, for user accounts.
|ID||Data Source||Data Component||Detects|
|DS0026||Active Directory||Active Directory Object Modification||
Monitor for changes made to AD security settings related to MFA logon requirements, such as changes to Azure AD Conditional Access Policies or the registration of new MFA applications.
|DS0015||Application Log||Application Log Content||
Enable security auditing to collect logs from hybrid identity solutions. For example, monitor sign-ins to the Azure AD Application Proxy Connector, which are typically generated only when a new Pass Through Authentication (PTA) Agent is added.  If AD FS is in use, review the logs for event ID 501, which specifies all EKU attributes on a claim, and raise alerts on any values that are not configured in your environment.
Monitor for suspicious additions to the
Monitor for suspicious modification of files associated with authentication processes, such as configuration files and module paths (e.g.
|DS0028||Logon Session||Logon Session Creation||
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.
Monitor for new, unfamiliar DLL files written to a domain controller and/or local computer. Password filters will also show up as an autorun and loaded DLL in lsass.exe. If AD FS is in use, monitor the AD FS server for the creation of DLLs as well as the loading of unrecognized or unsigned DLLs into the
|DS0009||Process||OS API Execution||
Monitor for calls to
Monitor for unexpected processes interacting with authentication mechanisms and processes to access user credentials or enable otherwise unwarranted access to accounts.
|DS0002||User Account||User Account Authentication||
Monitor for account authentications in which MFA credentials are not provided by the user account to the authenticating entity.
|User Account Modification||
Monitor for the enrollment of devices and user accounts with alternative security settings that do not require MFA credentials for successful logon.
|DS0024||Windows Registry||Windows Registry Key Modification||
Monitor for changes to Registry entries for password filters (ex: