Home/ATT&CK Technique/Pluggable Authentication Modules
ATT&CK Technique

Pluggable Authentication Modules

T1556.003 · defense-impairment, persistence, credential-access

Adversaries may modify pluggable authentication modules (PAM) to access user credentials or enable otherwise unwarranted access to accounts. PAM is a modular system of configuration files, libraries, and executable files which guide authentication for many services. The most common authentication module is pam_unix.so, which retrieves, sets, and verifies account authentication information in /etc/passwd and /etc/shadow.

Adversaries may modify components of the PAM system to create backdoors. PAM components, such as pam_unix.so, can be patched to accept arbitrary adversary supplied values as legitimate credentials. Malicious modifications to the PAM system may also be abused to steal credentials.

Adversaries may infect PAM resources with code to harvest user credentials, since the values exchanged with PAM components may be plain-text since PAM does not store passwords.

LinuxmacOS
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Actors Using This

1
chinaSalt Typhoon
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Atomic Tests

3
Executable Atomic Red Team test cases for exercising this technique in a lab. Copy a command, run it on the listed platform, confirm your detections fire.
shelevatedlinuxMalicious PAM rule
Inserts a rule into a PAM config and then tests it. Upon successful execution, this test will insert a rule that allows every user to su to root without a password. 
sudo sed -i "#{index}s,^,#{pam_rule}\n,g" #{path_to_pam_conf}
shelevatedlinuxMalicious PAM rule (freebsd)
Inserts a rule into a PAM config and then tests it. Upon successful execution, this test will insert a rule that allows every user to su to root without a password. 
sudo sed -i "" "#{index}s,^,#{pam_rule}\n,g" #{path_to_pam_conf}
shelevatedlinuxMalicious PAM module
Creates a PAM module, inserts a rule to use it, and then tests it. Upon successful execution, this test will create a PAM module that allows every user to su to root without a password. 
sudo sed -i "#{index}s,^,#{pam_rule}\n,g" #{path_to_pam_conf}
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Mitigations

2
MITRE ATT&CK mitigations - vendor-agnostic guidance for reducing exposure to this technique.
M1026Privileged Account Management

Privileged Account Management focuses on implementing policies, controls, and tools to securely manage privileged accounts (e.g., SYSTEM, root, or administrative accounts). This includes restricting access, limiting the scope of permissions, monitoring privileged account usage, and ensuring accountability through logging and auditing.

Account Permissions and Roles
  • Implement RBAC and least privilege principles to allocate permissions securely.
  • Use tools like Active Directory Group Policies to enforce access restrictions.
Credential Security
  • Deploy password vaulting tools like CyberArk, HashiCorp Vault, or KeePass for secure storage and rotation of credentials.
  • Enforce password policies for complexity, uniqueness, and expiration using tools like Microsoft Group Policy Objects (GPO).
Multi-Factor Authentication (MFA)
  • Enforce MFA for all privileged accounts using Duo Security, Okta, or Microsoft Azure AD MFA.
Privileged Access Management (PAM)
  • Use PAM solutions like CyberArk, BeyondTrust, or Thycotic to manage, monitor, and audit privileged access.
Auditing and Monitoring
  • Integrate activity monitoring into your SIEM (e.g., Splunk or QRadar) to detect and alert on anomalous privileged account usage.
Just-In-Time Access
  • Deploy JIT solutions like Azure Privileged Identity Management (PIM) or configure ephemeral roles in AWS and GCP to grant time-limited elevated permissions.
Tools for Implementation Privileged Access Management (PAM)
  • CyberArk, BeyondTrust, Thycotic, HashiCorp Vault.
Credential Management
  • Microsoft LAPS (Local Admin Password Solution), Password Safe, HashiCorp Vault, KeePass.
Multi-Factor Authentication
  • Duo Security, Okta, Microsoft Azure MFA, Google Authenticator.
Linux Privilege Management
  • sudo configuration, SELinux, AppArmor.
Just-In-Time Access
  • Azure Privileged Identity Management (PIM), AWS IAM Roles with session constraints, GCP Identity-Aware Proxy.
M1032Multi-factor Authentication

Multi-Factor Authentication (MFA) enhances security by requiring users to provide at least two forms of verification to prove their identity before granting access. These factors typically include: - Something you know: Passwords, PINs. - Something you have: Physical tokens, smartphone authenticator apps. - Something you are: Biometric data such as fingerprints, facial recognition, or retinal scans. Implementing MFA across all critical systems and services ensures robust protection against account takeover and unauthorized access.

Identity and Access Management (IAM)
  • Use IAM solutions like Azure Active Directory, Okta, or AWS IAM to enforce MFA policies for all user logins, especially for privileged roles.
  • Enable conditional access policies to enforce MFA for risky sign-ins (e.g., unfamiliar devices, geolocations).
  • Enable Conditional Access policies to only allow logins from trusted devices, such as those enrolled in Intune or joined via Hybrid/Entra.
Authentication Tools and Methods
  • Use authenticator applications such as Google Authenticator, Microsoft Authenticator, or Authy for time-based one-time passwords (TOTP).
  • Deploy hardware-based tokens like YubiKey, RSA SecurID, or smart cards for additional security.
  • Enforce biometric authentication for compatible devices and applications.
Secure Legacy Systems
  • Integrate MFA solutions with older systems using third-party tools like Duo Security or Thales SafeNet.
  • Enable RADIUS/NPS servers to facilitate MFA for VPNs, RDP, and other network logins.
Monitoring and Alerting
  • Use SIEM tools to monitor failed MFA attempts, login anomalies, or brute-force attempts against MFA systems.
  • Implement alerts for suspicious MFA activities, such as repeated failed codes or new device registrations.
Training and Policy Enforcement
  • Educate employees on the importance of MFA and secure authenticator usage.
  • Enforce policies that require MFA on all critical systems, especially for remote access, privileged accounts, and cloud applications.
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Detection Coverage

0/6 layers
Coverage across standard detection surfaces. Rows marked none have no rule of that type mapped. Some are real blind spots worth closing; others are simply not applicable to this technique (e.g. YARA matches malware files, not network behaviour).
Behavioral / log (Sigma) none
Analytics (MITRE CAR) none
Runtime / container (Falco) none
File / malware (YARA) none
Network (Suricata/Snort) none
Vuln scan (Nuclei) none
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Comply & Defend

NIST 800-53AC-02, AC-03, AC-05, AC-06, AC-07, AC-20, CM-05, CM-06, IA-02, IA-05, SI-04, SI-07
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