BlackHole2 Exploit Kit Detection

Hunt Hypothesis

The BlackHole2 Exploit Kit Detection identifies potential exploitation attempts by unusual network traffic patterns indicative of malicious payloads being exfiltrated. SOC teams should proactively hunt for this behavior in Azure Sentinel to detect and mitigate early-stage compromise by exploit kits that may lead to persistent threats.

YARA Rule

rule blackhole2_css : EK
{
meta:
   author = "Josh Berry"
   date = "2016-06-27"
   description = "BlackHole2 Exploit Kit Detection"
   hash0 = "9664a16c65782d56f02789e7d52359cd"
   sample_filetype = "js-html"
   yaragenerator = "https://github.com/Xen0ph0n/YaraGenerator"
strings:
   $string1 = "background:url('%%?a=img&img=countries.gif')"
   $string2 = "background:url('%%?a=img&img=exploit.gif')"
   $string3 = "background:url('%%?a=img&img=oses.gif')"
   $string4 = "background:url('%%?a=img&img=browsers.gif')"
   $string5 = "background:url('%%?a=img&img=edit.png')"
   $string6 = "background:url('%%?a=img&img=add.png')"
   $string7 = "background:url('%%?a=img&img=accept.png')"
   $string8 = "background:url('%%?a=img&img=del.png')"
   $string9 = "background:url('%%?a=img&img=stat.gif')"
condition:
   18 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 9 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: Scheduled system backup using Veeam Backup & Replication
  Filter/Exclusion: process.name != "vbm.exe" or process.name != "vbackup.exe"

• Scenario: Admin performing Windows Update via Group Policy
  Filter/Exclusion: process.name != "wuauclt.exe" or process.name != "msiexec.exe"

• Scenario: Running PowerShell scripts for routine system maintenance
  Filter/Exclusion: process.name != "powershell.exe" or script.name != "maintenance.ps1"

• Scenario: Log management tool like Splunk or ELK Stack collecting logs
  Filter/Exclusion: process.name != "splunkd.exe" or process.name != "logstash.jar"

• Scenario: Database backup job using SQL Server Agent
  Filter/Exclusion: process.name != "sqlservr.exe" or process.name != "sqlagent.exe"