hancitor dropper

Hunt Hypothesis

The hancitor dropper detection identifies potential malicious payload delivery by adversaries using a known malware distribution method, indicating possible initial compromise. SOC teams should proactively hunt for this behavior in Azure Sentinel to detect early-stage attacks and prevent lateral movement and data exfiltration.

YARA Rule

rule hancitor_dropper : vb_win32api
{
  meta:
    author = "Jeff White - jwhite@paloaltonetworks @noottrak"
    date   = "18AUG2016"
    hash1  = "03aef51be133425a0e5978ab2529890854ecf1b98a7cf8289c142a62de7acd1a"
    hash2  = "4b3912077ef47515b2b74bc1f39de44ddd683a3a79f45c93777e49245f0e9848"
    hash3  = "a78972ac6dee8c7292ae06783cfa1f918bacfe956595d30a0a8d99858ce94b5a"

  strings:
    $api_01 = { 00 56 69 72 74 75 61 6C 41 6C 6C 6F 63 00 }  // VirtualAlloc
    $api_02 = { 00 52 74 6C 4D 6F 76 65 4D 65 6D 6F 72 79 00 }  // RtlMoveMemory
    $api_04 = { 00 43 61 6C 6C 57 69 6E 64 6F 77 50 72 6F 63 41 00 }  // CallWindowProcAi
    $magic  = { 50 4F 4C 41 }  // POLA

  condition:
    uint32be(0) == 0xD0CF11E0 and all of ($api_*) and $magic
}

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

• Scenario: Scheduled System Maintenance Task
  Description: A legitimate scheduled task using schtasks.exe is running a script that mimics the behavior of a dropper.
  Filter/Exclusion: Check for schtasks.exe with a known maintenance task name or check the command line for --schedule or --trigger flags.

• Scenario: Admin Using PowerShell for Script Deployment
  Description: An administrator is using PowerShell (powershell.exe) to deploy a legitimate script that is being flagged due to similar code patterns.
  Filter/Exclusion: Filter by powershell.exe with a known script path or check for --executionpolicy or --command flags indicating a trusted script.

• Scenario: Software Update via Group Policy
  Description: A Group Policy Object (GPO) is triggering a script or executable that is being flagged as a dropper during a routine software update.
  Filter/Exclusion: Check for gpupdate.exe or gpo related processes, and verify the source path against a trusted update server.

• Scenario: Logon Script Execution
  Description: A user logon script (e.g., via logon.bat or logon.cmd) is being executed and matches the dropper pattern due to similar command-line arguments.
  Filter/Exclusion: Filter by cmd.exe or runonce.exe with a known logon script path, or check for --logon or --user flags.

• Scenario: Legitimate Binary with Similar Signature
  Description: A legitimate binary (e.g., msiexec.exe, regsvr32.exe) is being flagged due to a YARA rule that has a false positive match.
  Filter/Exclusion: Exclude known benign binaries by checking the full path or