PLINK8619841985

Hunt Hypothesis

This rule detects the presence of PLINK, a command-line tool frequently used by adversaries to establish remote connections or transfer files, often as part of lateral movement or initial access activities. Proactively hunting for this indicator in Azure Sentinel allows the SOC team to identify potential unauthorized remote access or data exfiltration attempts before they escalate into a full compromise.

YARA Rule

rule PLINK8619841985
{
      meta:
		author="malware-lu"
strings:
		$a0 = { FA 8C C7 8C D6 8B CC BA [2] 8E C2 26 }

condition:
		$a0 at pe.entry_point
}

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: An IT administrator uses plink.exe (PuTTY suite) to execute a remote PowerShell script on a Windows Server for a scheduled maintenance task (e.g., disk cleanup or log rotation).
  • Filter/Exclusion: Exclude processes where the parent process is cmd.exe or powershell.exe and the command line contains specific maintenance keywords like clean, rotate, or backup, or restrict the exclusion to specific service accounts (e.g., svc-maintenance).
• Scenario: A DevOps engineer uses plink.exe to push configuration changes to a Linux-based CI/CD runner or container host via SSH, where the remote command is a standard build or test script (e.g., npm run build or pytest).
  • Filter/Exclusion: Exclude executions where the remote command line matches common build/test patterns (e.g., npm, mvn, gradle, pytest, make) and the source user is part of the devops or ci-cd security group.
• Scenario: A database administrator uses plink.exe to connect to a remote SQL Server instance to run a quick sp_helpdb or index rebuild command for performance tuning.
  • Filter/Exclusion: Exclude processes where the command line contains SQL-specific verbs like sp_, rebuild, optimize, or backup and the target host is in the db-cluster subnet or has a hostname suffix like -sql.
• Scenario: A network engineer uses plink.exe to check the status of a remote network appliance (e.g., Juniper or Cisco router) by running a simple show version or display configuration command.
  • Filter/Exclusion: Exclude executions where the command line contains network status keywords like show, `