http://securityaffairs.co/wordpress/28170/cyber-crime/gholee-malware.html

Hunt Hypothesis

This hunt targets adversaries deploying Gholee malware to establish persistence and exfiltrate sensitive data through covert HTTP communications within the Azure environment. Proactively searching for these specific network patterns is critical because Gholee’s low-severity signature often evades standard alerting, allowing attackers to maintain a stealthy foothold before escalating their activities.

YARA Rule

rule MW_gholee_v2 : v2
{
meta:
        author = "@GelosSnake"
        date = "2015-02-12"
        description = "http://securityaffairs.co/wordpress/28170/cyber-crime/gholee-malware.html"
        hash0 = "05523761ca296ec09afdf79477e5f18d"
        hash1 = "08e424ac42e6efa361eccefdf3c13b21"
        hash2 = "5730f925145f1a1cd8380197e01d9e06"
        hash3 = "73461c8578dd9ab86d42984f30c04610"
        sample_filetype = "dll"
strings:
        $string0 = "RichHa"
        $string1 = "         (((((                  H" wide
        $string2 = "1$1,141<1D1L1T1\\1d1l1t1"
        $string3 = "<8;$O' "
        $string4 = "@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]"
        $string5 = "jYPQTVTSkllZTTXRTUiHceWda/"
        $string6 = "urn:schemas-microsoft-com:asm.v1"
        $string7 = "8.848H8O8i8s8y8"
        $string8 = "wrapper3" wide
        $string9 = "pwwwwwwww"
        $string10 = "Sunday"
        $string11 = "YYuTVWh"
        $string12 = "DDINGPADDINGXXPADDINGPADDINGXXPADDINGPADDINGXXPADDINGPADDINGXXPADDINGPADDINGXXPADDINGPADDINGXXPADDIN"
        $string13 = "ytMMMMMMUbbrrrrrxxxxxxxxrriUMMMMMMMMMUuzt"
        $string15 = "wrapper3 Version 1.0" wide
        $string16 = "77A779"
        $string17 = "<C<G<M<R<X<"
        $string18 = "9 9-9N9X9s9"
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 18 string patterns in its detection logic.

• Source Rule

False Positive Guidance

Based on the Gholee malware detection logic—which typically focuses on suspicious HTTP requests to known malicious domains, unusual User-Agent strings, or specific file execution patterns associated with this threat family—here are 5 specific false positive scenarios in a legitimate enterprise environment:

• Corporate Web Proxy and Caching Appliances

  • Scenario: Enterprise load balancers (e.g., F5 Big-IP) or web proxies (e.g., Squid, BlueCoat) often generate HTTP requests to external security intelligence feeds or update servers. These appliances may use generic User-Agent strings that lack the specific browser versioning expected by the rule, triggering a “suspicious agent” alert when accessing Gholee-associated domains for threat updates.
  • Filter/Exclusion: Create an exclusion filter based on the Source IP range of the proxy infrastructure and whitelist the specific Destination Domain (e.g., updates.security-vendor.com) if it is a known benign partner, or refine the User-Agent regex to accept standard appliance strings like F5-BigIP/12.0.

• Automated Backup and Migration Scripts

  • Scenario: Scheduled PowerShell scripts running on Windows Servers (e.g., via Task Scheduler) often utilize WinHTTP or Invoke-WebRequest to push logs or fetch configuration files from external cloud storage endpoints. If these scripts access a domain that shares an IP block with Gholee’s command-and-control infrastructure, the rule may flag the script’s HTTP traffic as anomalous due to non-standard headers.
  • Filter/Exclusion: Exclude Process Name patterns matching known automation tools (e.g., powershell.exe, python.exe) executing from a specific directory path (e.g., C:\Scripts\Backup\*) and whitelist the destination IP addresses associated with the enterprise’s cloud storage provider.

• **Endpoint Detection and Response