Ponmocup Downloader

Hunt Hypothesis

This detection targets adversaries utilizing the Ponmocup Downloader to establish initial footholds by retrieving and executing secondary payloads within the Azure environment. Proactive hunting for this behavior is essential to identify early-stage supply chain compromises or lateral movement attempts before they escalate into critical incidents, even when individual events are flagged as low severity.

YARA Rule

rule Trj_Ponmocup_Downloader {
        meta:
                author = "Centro Criptológico Nacional (CCN)"
                ref ="https://www.ccn-cert.cni.es/informes/informes-ccn-cert-publicos.html"
                description = "Ponmocup Downloader"
        strings:
                $mz = { 4d 5a }
                $vb5 = "VB5" fullword ascii
                $tpb = "www.thepiratebay.org" fullword wide
                $ua = "Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.2; SV1)" fullword wide
        condition:
                ($mz at 0) and ($vb5) and ($tpb) and ($ua)
}

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 5 specific false positive scenarios for the Ponmocup Downloader detection rule in an enterprise environment, along with recommended filters or exclusions:

• Scheduled Software Update via SCCM/Intune

  • Scenario: The Ponmocup Downloader is triggered during nightly maintenance windows when System Center Configuration Manager (SCCM) or Microsoft Intune pushes a mandatory application update to endpoint devices. The downloader executable runs as a background service to fetch the latest patch binaries, mimicking suspicious download activity.
  • Filter/Exclusion: Exclude processes where the parent process is ccmexec.exe (SCCM) or Microsoft.IntuneManagementExtension.exe, and restrict the rule to only trigger outside of defined maintenance windows (e.g., 02:00–06:00 UTC).

• Automated Backup Agent Initialization

  • Scenario: A legitimate backup agent, such as Veeam Agent for Windows or Commvault Simpana, initiates a pre-backup health check. This involves the Ponmocup Downloader fetching configuration manifests or incremental block maps from an internal repository server before the actual data transfer begins.
  • Filter/Exclusion: Create an exclusion based on the destination IP address range (e.g., 10.x.x.x for internal backup servers) and filter out events where the user context is a dedicated service account like NT AUTHORITY\SYSTEM or DOMAIN\VeeamSvc.

• IT Admin Manual Patch Deployment

  • Scenario: An IT administrator manually deploys a new security tool (e.g., CrowdStrike or SentinelOne) to a pilot group of workstations. The admin uses the Ponmocup Downloader utility to pull the installer package from an internal file share (\\FileServer\Deployments) rather than an external public URL, triggering the rule due to high network