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_htm : EK
{
meta:
   author = "Josh Berry"
   date = "2016-06-27"
   description = "BlackHole2 Exploit Kit Detection"
   hash0 = "92e21e491a90e24083449fd906515684"
   hash1 = "98b302a504a7ad0e3515ab6b96d623f9"
   hash2 = "a91d885ef4c4a0d16c88b956db9c6f43"
   hash3 = "d8336f7ae9b3a4db69317aea105f49be"
   hash4 = "eba5daf0442dff5b249274c99552177b"
   hash5 = "02d8e6daef5a4723621c25cfb766a23d"
   hash6 = "dadf69ce2124283a59107708ffa9c900"
   hash7 = "467199178ac940ca311896c7d116954f"
   hash8 = "17ab5b85f2e1f2b5da436555ea94f859"
   sample_filetype = "js-html"
   yaragenerator = "https://github.com/Xen0ph0n/YaraGenerator"
strings:
   $string0 = ">links/</a></td><td align"
   $string1 = ">684K</td><td>"
   $string2 = "> 36K</td><td>"
   $string3 = "move_logs.php"
   $string4 = "files/"
   $string5 = "cron_updatetor.php"
   $string6 = ">12-Sep-2012 23:45  </td><td align"
   $string7 = ">  - </td><td>"
   $string8 = "cron_check.php"
   $string9 = "-//W3C//DTD HTML 3.2 Final//EN"
   $string10 = "bhadmin.php"
   $string11 = ">21-Sep-2012 15:25  </td><td align"
   $string12 = ">data/</a></td><td align"
   $string13 = ">3.3K</td><td>"
   $string14 = "cron_update.php"
condition:
   14 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 15 string patterns in its detection logic.

Source Rule

False Positive Guidance

Scenario: System update or patching tool execution
Description: Legitimate system update tools (e.g., Windows Update, SCCM, or third-party patch managers) may trigger the rule due to similar network behavior or file hashes.
Filter/Exclusion: Exclude processes associated with known update tools (e.g., wusa.exe, setup.exe, ccmexec.exe) or filter by IP ranges used by enterprise update servers.
Scenario: Scheduled backup or data synchronization job
Description: Backup tools (e.g., Veeam, Acronis, or native Windows Backup) or data sync jobs (e.g., rsync, Syncthing) may exhibit behavior similar to exploit kit traffic, such as outbound connections to external servers.
Filter/Exclusion: Exclude connections to known backup or sync server IPs, or filter by process names associated with backup tools.
Scenario: Admin task using PowerShell or command-line tools
Description: Administrators may use PowerShell or command-line tools (e.g., powershell.exe, cmd.exe) to perform remote management, configuration changes, or script execution, which could resemble exploit kit activity.
Filter/Exclusion: Exclude processes initiated by admin accounts with known legitimate scripts or filter by user context (e.g., user = admin or user = service_account).
Scenario: Network monitoring or security tool traffic
Description: Security tools like Wireshark, tcpdump, or SIEM systems may generate traffic that matches the signature of the BlackHole2 Exploit Kit.
Filter/Exclusion: Exclude traffic from known security tool IPs or process names (e.g., wireshark.exe, tcpdump.exe, splunkd.exe).
Scenario: Cloud service integration or API calls
Description: Applications integrating with cloud services (e.g., AWS, Azure