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Detects EquationGroup Tool - April Leak

yara LOW Yara-Rules
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This rule was pulled from an open-source repository and enriched with AI. Validate in a test environment before deploying to production.
View original rule at Yara-Rules →
Retrieved: 2026-06-10T11:00:00Z · Confidence: medium

Hunt Hypothesis

The detection identifies potential use of the EquationGroup tool, specifically the April Leak variant, which may indicate advanced persistent threat activity. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify early signs of sophisticated malware execution and potential lateral movement within the network.

YARA Rule

rule EquationGroup_Toolset_Apr17_GrDo_FileScanner_Implant {
   meta:
      description = "Detects EquationGroup Tool - April Leak"
      author = "Florian Roth"
      reference = "https://steemit.com/shadowbrokers/@theshadowbrokers/lost-in-translation"
      date = "2017-04-15"
      hash1 = "8d2e43567e1360714c4271b75c21a940f6b26a789aa0fce30c6478ae4ac587e4"
   strings:
      $s1 = "system32\\winsrv.dll" fullword wide
      $s2 = "raw_open CreateFile error" fullword ascii
      $s3 = "\\dllcache\\" fullword wide
   condition:
      ( uint16(0) == 0x5a4d and filesize < 400KB and all of them )
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

This rule contains 3 string patterns in its detection logic.

References

False Positive Guidance

Original source: https://github.com/Yara-Rules/rules/blob/main/malware/APT_eqgrp_apr17.yar