PESpinv07Cyberbob

Hunt Hypothesis

This detection identifies the execution of the Cyberbob malware family via a specific YARA signature, signaling potential initial access or reconnaissance activities by an adversary leveraging this threat actor’s toolset. Proactive hunting for this indicator in Azure Sentinel is essential to uncover early-stage infections that may evade standard heuristic controls and prevent lateral movement before the low-severity alert escalates into a broader incident.

YARA Rule

rule PESpinv07Cyberbob
{
      meta:
		author="malware-lu"
strings:
		$a0 = { EB 01 68 60 E8 00 00 00 00 8B 1C 24 83 C3 12 81 2B E8 B1 06 00 FE 4B FD 82 2C 24 83 D5 46 00 0B E4 74 9E 75 01 C7 81 73 04 D7 7A F7 2F 81 73 19 77 00 43 B7 F6 C3 6B B7 00 00 F9 FF E3 C9 C2 08 00 A3 68 72 01 FF 5D 33 C9 41 E2 17 EB 07 EA EB 01 EB EB 0D FF }

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

Here are 5 specific false positive scenarios for the PESpinv07Cyberbob detection rule, along with recommended filters or exclusions tailored for an enterprise environment:

• Scenario: Automated Endpoint Protection Scans triggering on known security tools.

  • Context: The YARA rule may flag the background scanning processes of major EDR/Antivirus agents (e.g., CrowdStrike Falcon Sensor, Microsoft Defender Antivirus Service) as they load signature databases or perform real-time file integrity checks that mimic the “Cyberbob” behavior pattern.
  • Filter/Exclusion: Add a process exclusion for C:\Program Files\CrowdStrike\fs_qc.exe and C:\Windows\System32\defender\MsMpEng.exe. Configure the rule to ignore events where the parent process is svchost.exe running under the LocalSystem account.

• Scenario: Scheduled System Health and Inventory Jobs.

  • Context: Enterprise inventory tools like PDQ Deploy, SCCM (Configuration Manager), or SolarWinds Patch Management often execute scheduled jobs that spin up temporary agents to query hardware/software states, which can generate the specific byte patterns detected by this rule.
  • Filter/Exclusion: Create a time-based exclusion for events occurring between 02:00 and 04:00 UTC on weekdays where the process name contains PDQ or ccmexec.exe. Alternatively, exclude file paths under C:\ProgramData\Microsoft\MCC\ and C:\Program Files\PDQ Enterprise\.

• Scenario: Admin-Initiated Script Execution via Task Scheduler.

  • Context: System Administrators frequently run PowerShell or Python scripts (e.g., Get-CyberbobReport.ps1) to generate compliance reports. These scripts often invoke the specific binary or