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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: 2026-06-09T23:00:00Z · Confidence: medium

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_DllLoad_Target {
   meta:
      description = "Detects EquationGroup Tool - April Leak"
      author = "Florian Roth"
      reference = "https://steemit.com/shadowbrokers/@theshadowbrokers/lost-in-translation"
      date = "2017-04-15"
      hash1 = "a42d5201af655e43cefef30d7511697e6faa2469dc4a74bc10aa060b522a1cf5"
   strings:
      $s1 = "BzWKJD+" fullword ascii

      $op1 = { 44 24 6c 6c 88 5c 24 6d }
      $op2 = { 44 24 54 63 c6 44 24 55 74 c6 44 24 56 69 }
      $op3 = { 44 24 5c 6c c6 44 24 5d 65 c6 44 24 5e }
   condition:
      ( uint16(0) == 0x5a4d and filesize < 200KB and all 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