pos jack

Hunt Hypothesis

This detection identifies Point-of-Sale (POS) memory scraping activities where adversaries inject malicious code to capture unencrypted payment card data during transaction processing. Proactively hunting for this behavior in Azure Sentinel is critical because early identification of these subtle memory manipulations allows the SOC team to isolate compromised terminals before sensitive financial information is exfiltrated, mitigating potential regulatory and reputational impact.

YARA Rule

rule pos_jack
{
meta:
	author = "@patrickrolsen"
	maltype = "Point of Sale (POS) Malware"
	version = "0.1"
	reference = "http://blog.spiderlabs.com/2014/02/jackpos-the-house-always-wins.html"
	date = "2/22/2014"
strings:
	$pdb1 = "\\ziedpirate.ziedpirate-PC\\"
	$pdb2 = "\\sop\\sop\\"
condition:
	uint16(0) == 0x5A4D and 1 of ($pdb*)
}

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 2 string patterns in its detection logic.

References

• http://blog.spiderlabs.com/2014/02/jackpos-the-house-always-wins.html
• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the pos_jack detection rule in an enterprise environment, including suggested filters and exclusions:

• Legacy Point-of-Sale Firmware Updates

  • Scenario: Scheduled overnight maintenance tasks performed by the NCR Silver or Oracle MICROS management console to push firmware patches to physical POS terminals. These updates often involve writing executable binaries directly to the C:\Program Files\POS_Terminal directory, mimicking the behavior of a rogue device connection.
  • Filter/Exclusion: Create an exclusion for processes originating from the specific service account (e.g., svc_pos_updater) running on the POS management server, specifically targeting file paths containing \FirmwareUpdates\.

• Endpoint Antivirus Real-Time Scanning

  • Scenario: The CrowdStrike Falcon or SentinelOne agent performing deep heuristic scans on the local storage of retail terminals. During peak hours, these agents may spawn temporary worker processes to analyze large transaction log files, triggering the pos_jack signature due to high I/O activity and process injection patterns similar to a POS jack connection.
  • Filter/Exclusion: Exclude known antivirus vendor executables (e.g., C:\Program Files\CrowdStrike\csagent.exe, SentinelOne\SentinelService.exe) from the rule’s scope, or filter out events where the parent process is identified as a security agent.

• Automated Inventory & Payment Reconciliation Scripts

  • Scenario: PowerShell scripts executed via Windows Task Scheduler (e.g., Daily_Inventory_Recon.ps1) that interface with legacy payment gateways like Verifone. These scripts often spawn child processes to read/write to COM ports or simulate hardware handshakes, which the YARA rule interprets as a physical POS jack event.