priv03

Hunt Hypothesis

This detection identifies potential unauthorized privilege escalation or lateral movement attempts by monitoring specific file artifacts defined in the priv03 YARA signature within Azure Sentinel workloads. A proactive hunt is essential to validate these low-severity signals against baseline activity, ensuring that subtle indicators of early-stage compromise are not overlooked before they evolve into critical incidents.

YARA Rule

rule priv03 {
 meta:
    date = "2018-02-10"
    author = "@unixfreaxjp"
 strings:
    $varb01 = { 41 57 41 56 41 55 41 54 55 53 0F B6 06 }
    $varb02 = { 48 C7 07 00 00 00 00 48 C7 47 08 00 00 }
    $vard01 = { 55 48 89 E5 41 57 41 56 41 55 41 54 53 }
    $vard02 = { 55 48 89 E5 48 C7 47 08 00 00 00 00 48 }
    // can be added
 condition:
    (2 of ($varb*)) or (2 of ($vard*))
}

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 4 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the priv03 detection rule in an enterprise environment, along with suggested filters or exclusions:

• Endpoint Protection Agent Updates

  • Scenario: The CrowdStrike Falcon or Microsoft Defender for Endpoint agents perform scheduled signature and engine updates. These processes often execute under high-privilege system accounts (e.g., NT AUTHORITY\SYSTEM or the specific service account) and spawn child processes that match the priv03 YARA signatures due to their elevated token usage during installation.
  • Filter/Exclusion: Exclude process paths matching known security vendor update installers, such as C:\Program Files\CrowdStrike\*\csagent.exe or C:\ProgramData\Microsoft\Windows Defender\Platform\*\MpCmdRun.exe, specifically when the parent process is a scheduled task runner (Task Scheduler).

• Patch Management Deployment (WSUS/SCCM)

  • Scenario: During monthly maintenance windows, Windows Server Update Services (WSUS) or Microsoft Endpoint Configuration Manager (MECM/SCCM) pushes critical OS patches. The deployment client (ccmexec.exe) runs with administrative privileges to install updates, triggering the rule when it modifies system binaries or registry keys associated with privilege escalation logic.
  • Filter/Exclusion: Create an exclusion for the ccmexec.exe process path (e.g., C:\Windows\CCM\*) and any child processes spawned by the “Software Center” scheduled task, provided the execution time falls within the defined maintenance window (e.g., Sundays 02:00–06:00 UTC).

• Identity Management Service Replication

  • Scenario: In Active Directory environments, the DirSync or Azure AD Connect service performs synchronization jobs. These services run under dedicated service accounts with local administrator rights and