Detects EquationGroup Tool - April Leak

Hunt Hypothesis

The hypothesis is that the detection of EquationGroup Tool - April Leak indicates potential adversary use of legacy malware with known persistence mechanisms. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate long-term threats that may have evaded traditional detection methods.

YARA Rule

rule EquationGroup_Toolset_Apr17_Eternalromance_2 {
   meta:
      description = "Detects EquationGroup Tool - April Leak"
      author = "Florian Roth"
      reference = "https://steemit.com/shadowbrokers/@theshadowbrokers/lost-in-translation"
      date = "2017-04-15"
      super_rule = 1
      hash1 = "f1ae9fdbb660aae3421fd3e5b626c1e537d8e9ee2f9cd6d56cb70b6878eaca5d"
      hash2 = "b99c3cc1acbb085c9a895a8c3510f6daaf31f0d2d9ccb8477c7fb7119376f57b"
      hash3 = "92c6a9e648bfd98bbceea3813ce96c6861487826d6b2c3d462debae73ed25b34"
   strings:
      $x1 = "[+] Backdoor shellcode written" fullword ascii
      $x2 = "[*] Attempting exploit method %d" fullword ascii
   condition:
      ( uint16(0) == 0x5a4d and filesize < 600KB and 1 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 2 string patterns in its detection logic.

References

• https://steemit.com/shadowbrokers/@theshadowbrokers/lost-in-translation
• Source Rule

False Positive Guidance

• Scenario: Legitimate system update via Windows Update
  Filter/Exclusion: process.name != "wusa.exe" or process.name != "setup.exe"

• Scenario: Scheduled backup job using Veeam Backup & Replication
  Filter/Exclusion: process.name != "veeambackup.exe" or process.parent.name != "services.exe"

• Scenario: Admin performing disk cleanup using Disk Cleanup tool
  Filter/Exclusion: process.name != "cleanmgr.exe" or process.parent.name != "explorer.exe"

• Scenario: Running a legitimate malware analysis tool like Cuckoo Sandbox
  Filter/Exclusion: process.name != "cuckoo.exe" or process.parent.name != "sandboxd.exe"

• Scenario: Automated log analysis using Splunk or ELK stack
  Filter/Exclusion: process.name != "splunkd.exe" or process.name != "java.exe" (with specific JAR file names)