BamBamv001Bedrock

Hunt Hypothesis

This rule detects the presence of the BamBam ransomware strain, a known threat actor that typically leverages PowerShell or batch scripts to encrypt files and establish persistence. Proactively hunting for this signature allows the SOC team to identify early-stage infections or dormant payloads in Azure environments before the ransomware executes its encryption routine and disrupts operations.

YARA Rule

rule BamBamv001Bedrock
{
      meta:
		author="malware-lu"
strings:
		$a0 = { 6A 14 E8 9A 05 00 00 8B D8 53 68 FB [2] 00 E8 6C FD FF FF B9 05 00 00 00 8B F3 BF FB [2] 00 53 F3 A5 E8 8D 05 00 00 8B 3D 03 [2] 00 A1 2B [2] 00 66 8B 15 2F [2] 00 B9 80 [2] 00 2B CF 89 45 E8 89 0D 6B [2] 00 66 89 55 EC 8B 41 3C 33 D2 03 C1 }

condition:
		$a0
}

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: A DevOps engineer uses Ansible or Terraform to provision new Windows Server instances, where the initialization scripts (e.g., bootstrap.ps1 or init.sh) contain inline base64-encoded configuration blocks or embedded YARA signatures for self-testing.
  • Filter/Exclusion: Exclude processes where the parent process is ansible-playbook.exe, terraform.exe, or powershell.exe launched by python.exe/node.exe (CI/CD agents), and limit the path to standard CI/CD working directories (e.g., C:\Jenkins\workspace\, C:\AzureDevOps\).
• Scenario: An IT administrator runs a custom PowerShell script to audit endpoint security configurations, which includes a step to download and execute a lightweight YARA scanner (e.g., yara64.exe) to verify that specific detection rules (like BamBamv001Bedrock) are present in the local rule set.
  • Filter/Exclusion: Exclude executions where the parent process is powershell.exe or pwsh.exe and the command line contains arguments like -Rule, scan, or verify, or where the working directory is a known admin utility folder (e.g., C:\AdminTools\, C:\Scripts\).
• Scenario: A security team deploys CrowdStrike Falcon or Carbon Black agents, and the agent’s background service (FalconService.exe or cb.exe) periodically loads YARA rules from its local cache directory to perform continuous memory scanning.
  • Filter/Exclusion: Exclude processes where the parent process is a known EDR agent service (e.g., FalconService.exe, cb.exe, defender.exe) and the file path resides within the vendor’s