Modification of Standard Authentication Module or Configuration

Elastic Stack Serverless Security

Adversaries may modify the standard authentication module for persistence via patching the normal authorization process or modifying the login configuration to allow unauthorized access or elevate privileges.

Rule type: query

Rule indices:

• auditbeat-*
• logs-endpoint.events.*

Severity: medium

Risk score: 47

Runs every: 5m

Searches indices from: now-9m (https://www.elastic.co/guide/en/elasticsearch/reference/current/common-options.html#date-math[Date Math format], see also Additional look-back time)

Maximum alerts per execution: 100

References:

• https://github.com/zephrax/linux-pam-backdoor
• https://github.com/eurialo/pambd
• http://0x90909090.blogspot.com/2016/06/creating-backdoor-in-pam-in-5-line-of.html
• https://www.trendmicro.com/en_us/research/19/i/skidmap-linux-malware-uses-rootkit-capabilities-to-hide-cryptocurrency-mining-payload.html

Tags:

• Elastic
• Host
• macOS
• Linux
• Threat Detection
• Credential Access
• Persistence

Version: 100

Rule authors:

• Elastic

Rule license: Elastic License v2

event.category:file and event.type:change and
  (file.name:pam_*.so or file.path:(/etc/pam.d/* or /private/etc/pam.d/*)) and
  process.executable:
    (* and
      not
      (
        /bin/yum or
        "/usr/sbin/pam-auth-update" or
        /usr/libexec/packagekitd or
        /usr/bin/dpkg or
        /usr/bin/vim or
        /usr/libexec/xpcproxy or
        /usr/bin/bsdtar or
        /usr/local/bin/brew or
        /usr/bin/rsync or
        /usr/bin/yum or
        /var/lib/docker/*/bin/yum or
        /var/lib/docker/*/bin/dpkg or
        ./merged/var/lib/docker/*/bin/dpkg or
        "/System/Library/PrivateFrameworks/PackageKit.framework/Versions/A/XPCServices/package_script_service.xpc/Contents/MacOS/package_script_service"
      )
    ) and
  not file.path:
         (
           /tmp/snap.rootfs_*/pam_*.so or
           /tmp/newroot/lib/*/pam_*.so or
           /private/var/folders/*/T/com.apple.fileprovider.ArchiveService/TemporaryItems/*/lib/security/pam_*.so or
           /tmp/newroot/usr/lib64/security/pam_*.so
         )

Framework: MITRE ATT&CKTM

• Tactic:

  • Name: Persistence
  • ID: TA0003
  • Reference URL: https://attack.mitre.org/tactics/TA0003/

• Technique:

  • Name: Create or Modify System Process
  • ID: T1543
  • Reference URL: https://attack.mitre.org/techniques/T1543/

• Tactic:

  • Name: Credential Access
  • ID: TA0006
  • Reference URL: https://attack.mitre.org/tactics/TA0006/

• Technique:

  • Name: Modify Authentication Process
  • ID: T1556
  • Reference URL: https://attack.mitre.org/techniques/T1556/