md5 87cf8209494eedd936b28ff620e28780

Hunt Hypothesis

The detection rule identifies potential malicious activity associated with the MD5 hash 87cf8209494eedd936b28ff620e28780, which may indicate the presence of unknown or evolving threats. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate potential compromise early, especially since the rule lacks MITRE technique mapping and may represent a previously unseen adversary tactic.

YARA Rule

rule md5_87cf8209494eedd936b28ff620e28780 {
    strings: $ = "curl_close($cu);eval($o);};die();"
    condition: any of them
}

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
• Source Rule

False Positive Guidance

• Scenario: A system update or patching tool (e.g., Windows Update, Microsoft Endpoint Manager) uses a known legitimate binary with the MD5 hash 87cf8209494eedd936b28ff620e28780 during deployment.
  Filter/Exclusion: Check for process parent or command line arguments containing WindowsUpdate, wuauclt.exe, or Microsoft Endpoint Manager related strings.

• Scenario: A backup or synchronization tool (e.g., Veeam, rsync, or Azure Backup) temporarily uses a binary with the same MD5 hash during data transfer or job execution.
  Filter/Exclusion: Filter events where the process is associated with backup tools or scheduled jobs named VeeamBackup, rsync, or AzureBackup.

• Scenario: A system administration task (e.g., schtasks.exe or Task Scheduler) runs a legitimate script or executable with the MD5 hash 87cf8209494eedd936b28ff620e28780 as part of a scheduled maintenance job.
  Filter/Exclusion: Exclude processes launched by schtasks.exe or with a command line containing Task Scheduler or scheduled task.

• Scenario: A software deployment tool (e.g., SCCM, Microsoft Intune, or Ansible) includes a legitimate file with the MD5 hash during package distribution.
  Filter/Exclusion: Filter based on the presence of SCCM, Intune, or Ansible in the process name or command line.

• Scenario: A legitimate security tool (e.g., Microsoft Defender, CrowdStrike, or Palo Alto Networks) uses a file with the MD5 hash during signature updates or integrity checks.
  **Filter/Ex