BlackHole2 Exploit Kit Detection

Hunt Hypothesis

The hypothesis is that the detection identifies potential exploitation attempts by the BlackHole2 Exploit Kit, which is commonly used to deliver malware through compromised websites. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage attacks before they lead to data exfiltration or system compromise.

YARA Rule

rule blackhole2_jar2 : EK
{
meta:
   author = "Josh Berry"
   date = "2016-06-27"
   description = "BlackHole2 Exploit Kit Detection"
   hash0 = "add1d01ba06d08818ff6880de2ee74e8"
   sample_filetype = "unknown"
   yaragenerator = "https://github.com/Xen0ph0n/YaraGenerator"
strings:
   $string0 = "6_O6d09"
   $string1 = "juqirvs.classPK"
   $string2 = "hw.classPK"
   $string3 = "a.classPK"
   $string4 = "w.classuS]w"
   $string5 = "w.classPK"
   $string6 = "YE}0vCZ"
   $string7 = "v)Q,Ff"
   $string8 = "%8H%t("
   $string9 = "hw.class"
   $string10 = "a.classmV"
   $string11 = "2CniYFU"
   $string12 = "juqirvs.class"
condition:
   12 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 13 string patterns in its detection logic.

• Source Rule

False Positive Guidance

• Scenario: Scheduled System Maintenance Job
  Description: A legitimate system maintenance job (e.g., task scheduler or cron job) is executing a script that includes payloads similar to those used by BlackHole2.
  Filter/Exclusion: Check the process owner and command line arguments. Exclude tasks with owner = SYSTEM or command_line LIKE '%schtasks%' or '%crontab%'.

• Scenario: Admin Tool for Patch Management
  Description: An administrator is using a legitimate patch management tool (e.g., Windows Update, WSUS, or Microsoft Endpoint Manager) that includes scripts or binaries with similar signatures to BlackHole2.
  Filter/Exclusion: Exclude processes with process_name = 'wuauserv.exe' or process_name = 'svchost.exe' and check for known patch management tools in the command line.

• Scenario: Log Collection and Analysis Tool
  Description: A log collection tool (e.g., Splunk, ELK Stack, or Graylog) is ingesting logs that include payloads or strings matching the BlackHole2 exploit kit.
  Filter/Exclusion: Exclude processes associated with log collection tools (e.g., splunkd.exe, logstash, graylog-server) or filter by source IP or log type.

• Scenario: Internal Code Signing or Binary Signing Tool
  Description: A developer is using a code signing tool (e.g., SignTool, codesign, or signtool.exe) to sign internal binaries, which may include strings that match the BlackHole2 signature.
  Filter/Exclusion: Exclude processes with process_name = 'signtool.exe' or process_name = 'codesign' and verify the digital signature of the binary.

• **Scenario