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T1556 Modify Authentication Process

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.

Item Value
ID T1556
Sub-techniques T1556.001, T1556.002, T1556.003, T1556.004, T1556.005, T1556.006, T1556.007, T1556.008
Tactics TA0006, TA0005, TA0003
Platforms Azure AD, Google Workspace, IaaS, Linux, Network, Office 365, SaaS, Windows, macOS
Version 2.3
Created 11 February 2020
Last Modified 11 April 2023

Procedure Examples

ID Name Description
S0377 Ebury Ebury can intercept private keys using a trojanized ssh-add function.15
S0487 Kessel Kessel has trojanized the ssh_login and user-auth_pubkey functions to steal plaintext credentials.16
S0692 SILENTTRINITY SILENTTRINITY can create a backdoor in KeePass using a malicious config file and in TortoiseSVN using a registry hook.14


ID Mitigation Description
M1047 Audit Review authentication logs to ensure that mechanisms such as enforcement of MFA are functioning as intended.
M1032 Multi-factor Authentication 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 (C:\Windows\System32\ by default) of a domain controller and/or local computer with a corresponding entry in HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\Notification Packages.
M1027 Password Policies Ensure that AllowReversiblePasswordEncryption property is set to disabled unless there are application requirements.9
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. 11 12 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. 13
M1025 Privileged Process Integrity Enabled features, such as Protected Process Light (PPL), for LSA.6
M1022 Restrict File and Directory Permissions Restrict write access to the /Library/Security/SecurityAgentPlugins directory.
M1024 Restrict Registry Permissions Restrict Registry permissions to disallow the modification of sensitive Registry keys such as HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\NetworkProvider\Order.
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
DS0026 Active Directory Active Directory Object Modification
DS0015 Application Log Application Log Content
DS0022 File File Creation
DS0028 Logon Session Logon Session Creation
DS0011 Module Module Load
DS0009 Process OS API Execution
DS0002 User Account User Account Authentication
DS0024 Windows Registry Windows Registry Key Creation


  1. Bialek, J. (2013, September 15). Intercepting Password Changes With Function Hooking. Retrieved November 21, 2017. 

  2. Chris Ross. (2018, October 17). Persistent Credential Theft with Authorization Plugins. Retrieved April 22, 2021. 

  3. Dell SecureWorks. (2015, January 12). Skeleton Key Malware Analysis. Retrieved April 8, 2019. 

  4. Metcalf, S. (2015, November 22). Dump Clear-Text Passwords for All Admins in the Domain Using Mimikatz DCSync. Retrieved November 15, 2021. 

  5. Microsoft. (2016, April 15). Audit Policy Recommendations. Retrieved June 3, 2016. 

  6. Microsoft. (2013, July 31). Configuring Additional LSA Protection. Retrieved February 13, 2015. 

  7. Microsoft Threat Intelligence Center, Microsoft Detection and Response Team, Microsoft 365 Defender Research Team . (2022, August 24). MagicWeb: NOBELIUM’s post-compromise trick to authenticate as anyone. Retrieved September 28, 2022. 

  8. Mike Burns. (2020, September 30). Detecting Microsoft 365 and Azure Active Directory Backdoors. Retrieved September 28, 2022. 

  9. Microsoft. (2021, October 28). Store passwords using reversible encryption. Retrieved January 3, 2022. 

  10. Microsoft. (2023, January 26). Policy CSP - WindowsLogon. Retrieved March 30, 2023. 

  11. Microsoft. (2016, April 15). Attractive Accounts for Credential Theft. Retrieved June 3, 2016. 

  12. Microsoft. (2016, April 16). Implementing Least-Privilege Administrative Models. Retrieved June 3, 2016. 

  13. Plett, C., Poggemeyer, L. (12, October 26). Securing Privileged Access Reference Material. Retrieved April 25, 2017. 

  14. Salvati, M. (2019, August 6). SILENTTRINITY Modules. Retrieved March 24, 2022. 

  15. M.Léveillé, M.. (2014, February 21). An In-depth Analysis of Linux/Ebury. Retrieved April 19, 2019. 

  16. Dumont, R., M.Léveillé, M., Porcher, H. (2018, December 1). THE DARK SIDE OF THE FORSSHE A landscape of OpenSSH backdoors. Retrieved July 16, 2020. 

  17. Microsoft. (2021, October 21). NPLogonNotify function (npapi.h). Retrieved March 30, 2023.