DES [long]

Hunt Hypothesis

The detection rule identifies potential adversary behavior involving data exfiltration through long-running, suspiciously sized data transfers, which may indicate covert data extraction. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage data exfiltration attempts that may evade traditional detection methods.

YARA Rule

rule DES_Long
{	meta:
		author = "_pusher_"
		date = "2015-05"
		description = "DES [long]"
	strings:
		$c0 = { 10 80 10 40 00 00 00 00 00 80 10 00 00 00 10 40 10 00 00 40 10 80 00 00 00 80 00 40 00 80 10 00 00 80 00 00 10 00 10 40 10 00 00 00 00 80 00 40 10 00 10 00 00 80 10 40 00 00 10 40 10 00 00 00 }
	condition:
		$c0
}

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: Scheduled System Maintenance Task
  Description: A legitimate system maintenance task (e.g., Windows Task Scheduler job) is running and generating DES traffic.
  Filter/Exclusion: process.name != "schtasks.exe" OR process.name != "task scheduler" or check for process.parent.name == "task scheduler" and exclude known maintenance tasks.

• Scenario: Database Backup Job
  Description: A database backup job (e.g., using sqlbackup.exe or mysqldump) is executing and generating DES-related activity.
  Filter/Exclusion: process.name != "sqlbackup.exe" OR process.name != "mysqldump" or use process.parent.name == "sqlservr.exe" to identify backup processes.

• Scenario: Admin User Performing Configuration Changes
  Description: An admin user (e.g., Administrator or root) is making configuration changes that involve DES activity (e.g., modifying group policies or registry keys).
  Filter/Exclusion: user.name != "Administrator" OR user.name != "root" or use user.privilege == "admin" and apply a whitelist of known admin activities.

• Scenario: Log File Rotation or Archiving
  Description: A log rotation tool (e.g., logrotate, rsyslog, or logrotate.exe) is archiving or rotating log files, which may trigger DES activity.
  Filter/Exclusion: process.name != "logrotate" OR process.name != "rsyslog" OR process.name != "logrotate.exe" or check for process.parent.name == "systemd" or process.parent.name == "init".

• Scenario: Security Software Performing Scans
  Description: Antivirus or endpoint protection software (e.g., Windows Defender, Bitdefender, `K