md5 6eb201737a6ef3c4880ae0b8983398a9

Hunt Hypothesis

The detection rule identifies potential malicious activity associated with the MD5 hash 6eb201737a6ef3c4880ae0b8983398a9, which may indicate the presence of known or emerging threats. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate potential compromise early, especially given the low severity threshold which may mask more advanced persistent threats.

YARA Rule

rule md5_6eb201737a6ef3c4880ae0b8983398a9 {
    strings:
        $ = "if(md5(@$_COOKIE[qz])=="
        $ = "($_=@$_REQUEST[q]).@$_($_REQUEST[z]);"
    condition: all 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

This rule contains 1 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: A system backup tool (e.g., Veeam Backup & Replication) is using a known legitimate binary with the MD5 hash 6eb201737a6ef3c4880ae0b8983398a9 during a scheduled backup job.
  Filter/Exclusion: Check for processes associated with backup tools (e.g., veeam.exe, vbragent.exe) or filter by process names containing “backup” or “snapshot”.

• Scenario: A patching tool (e.g., Microsoft Update or SCCM) is executing a legitimate update package that matches the MD5 hash.
  Filter/Exclusion: Filter by processes related to patching tools (e.g., wusa.exe, ccmexec.exe) or check for known update-related MD5 hashes in a whitelist.

• Scenario: A system monitoring tool (e.g., Nagios or Zabbix) is using a custom plugin or script with the same MD5 hash for data collection.
  Filter/Exclusion: Exclude processes associated with monitoring tools (e.g., nagios.exe, zabbix_agentd.exe) or filter by file paths in known monitoring directories.

• Scenario: A scheduled system cleanup task (e.g., Windows Task Scheduler running cleanmgr.exe) is using a legitimate file with the same MD5 hash.
  Filter/Exclusion: Filter by process names like cleanmgr.exe or check for execution context from the Task Scheduler.

• Scenario: A database backup utility (e.g., MySQL mysqldump) is generating a temporary file with the same MD5 hash during a backup operation.
  Filter/Exclusion: Exclude files created in temporary directories (e.g., C:\Users\Public\Temp) or filter by process names related to database utilities.