PseudoSigner01PENightMare2BetaAnorganix

Hunt Hypothesis

This detection identifies potential NightMare campaign activity by flagging executables with suspicious pseudo-signing characteristics that mimic legitimate software to evade standard signature-based defenses. A proactive hunt is essential in Azure Sentinel to uncover stealthy initial access attempts where adversaries leverage forged digital signatures to establish a foothold before triggering high-severity alerts.

YARA Rule

rule PseudoSigner01PENightMare2BetaAnorganix
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 60 E9 10 00 00 00 EF 40 03 A7 07 8F 07 1C 37 5D 43 A7 04 B9 2C 3A E9 }

condition:
		$a0 at pe.entry_point
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

• Microsoft Defender for Endpoint — Custom indicators / advanced hunting
• Email Gateway — Attachment scanning
• File Share Monitoring — Periodic scanning of shared drives
• YARA CLI — Manual threat hunting on endpoints

This rule contains 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the PseudoSigner01PENightMare2BetaAnorganix detection rule, tailored to a legitimate enterprise environment:

• Scenario: Automated Endpoint Protection Scans

  • Context: During off-hours (e.g., 02:00–04:00), the CrowdStrike Falcon or Microsoft Defender for Endpoint agent performs its scheduled “On-Demand Scan” of the C:\Program Files directory. The YARA signature may flag the scanning engine’s temporary extraction of a signed binary as an anomaly if the rule expects specific signing metadata that varies during the scan process.
  • Suggested Filter/Exclusion: Exclude processes matching C:\ProgramData\Microsoft\Windows Defender\Platform\<version>\mpcmd.dll (or equivalent CrowdStrike path) when running with command line arguments containing /scan or /full.

• Scenario: Scheduled Patch Deployment via SCCM

  • Context: The enterprise utilizes Microsoft Endpoint Configuration Manager (MECM/SCCM) to push Windows updates and application patches nightly. When the ccmsetup.exe service installs a new update package, it extracts signed components that may trigger the “NightMare” logic due to temporary file creation patterns in %TEMP% that mimic the rule’s anomaly detection criteria.
  • Suggested Filter/Exclusion: Create an exclusion for the process ccmsetup.exe and its child processes running under the SYSTEM account, specifically when the execution path contains \Microsoft Endpoint Configuration Manager\.

• Scenario: Backup Agent Data Indexing

  • Context: The Veeam Backup & Replication agent runs a nightly “Catalog Update” job to index restored data. This process involves reading and validating thousands of signed files, which can generate high-volume file