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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 hunt hypothesis detects potential adversary 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 and mitigate early-stage compromise by sophisticated adversaries leveraging known malware.

YARA Rule

rule EquationGroup_Toolset_Apr17_xxxRIDEAREA {
   meta:
      description = "Detects EquationGroup Tool - April Leak"
      author = "Florian Roth"
      reference = "https://steemit.com/shadowbrokers/@theshadowbrokers/lost-in-translation"
      date = "2017-04-15"
      hash1 = "214b0de83b04afdd6ad05567825b69663121eda9e804daff9f2da5554ade77c6"
   strings:
      $x1 = "USAGE: %s -i InputFile -o OutputFile [-f FunctionOrdinal] [-a FunctionArgument] [-t ThreadOption]" fullword ascii
      $x2 = "The output payload \"%s\" has a size of %d-bytes." fullword ascii
      $x3 = "ERROR: fwrite(%s) failed on ucPayload" fullword ascii
      $x4 = "Load and execute implant within the existing thread" fullword ascii
   condition:
      ( uint16(0) == 0x5a4d and filesize < 200KB and 1 of them )
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

This rule contains 4 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