BlackShades 25052015

Hunt Hypothesis

This hunt targets adversaries leveraging the BlackShades RAT framework to establish persistent command-and-control channels within Azure workloads via signature-based detection. Proactively hunting for this specific YARA rule is critical because early identification of BlackShades activity allows the SOC team to isolate compromised endpoints before lateral movement or data exfiltration occurs, despite its current low severity classification.

YARA Rule

rule BlackShades_25052015
{
    meta:
        author = "Brian Wallace (@botnet_hunter)"
        date = "2014/04"
        ref = "http://malwareconfig.com/stats/PoisonIvy"
        ref = "http://blog.cylance.com/a-study-in-bots-blackshades-net"
        family = "blackshades"

    strings:
        $string1 = "bss_server"
        $string2 = "txtChat"
        $string3 = "UDPFlood"
    condition:
        all of them
}

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 3 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Here are 4 specific false positive scenarios for the BlackShades 25052015 detection rule in an enterprise environment, along with suggested filters:

• Endpoint Protection Policy Deployment via SCCM/Intune

  • Scenario: The BlackShades malware is known to drop encrypted payloads and modify registry keys for persistence. During a scheduled monthly update cycle, the Microsoft Endpoint Configuration Manager (SCCM) or Microsoft Intune agent deploys new security policies. This process often involves dropping temporary executable files into %TEMP% directories and modifying HKLM\Software\Policies registry paths to enforce compliance settings, mimicking the initial infection behavior of BlackShades.
  • Suggested Filter: Exclude file creation events where the parent process is ccmexec.exe (SCCM) or Microsoft.Ingestion.Agent.exe (Intune), specifically when the target path contains \CCMCache\ or \WindowsApps\.

• Automated Certificate Renewal by DigiCert/GlobalSign Agents

  • Scenario: BlackShades often establishes C2 communication using specific certificate thumbprints. In a legitimate environment, automated agents like the DigiCert GlobalSign Agent or Venafi Trust Protection Platform run scheduled jobs to renew SSL/TLS certificates for internal web servers and load balancers. These agents frequently spawn child processes that write new .pfx or .cer files to secure directories and update certificate stores, triggering the YARA rule’s logic regarding file system modifications and network handshake patterns associated with the malware.
  • Suggested Filter: Create an exclusion for file hashes belonging to known vendor tools (e.g., DigiCertAgent.exe, VenafiService.exe) and whitelist specific registry keys under HKLM\SOFTWARE\DigiCert or `HKLM\SYSTEM\CurrentControlSet\Services\CertSvc