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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 sophisticated malware associated with advanced persistent threats. SOC teams should proactively hunt for this behavior in Azure Sentinel to identify and mitigate early-stage compromise by threat actors leveraging known malicious tooling.

YARA Rule

rule EquationGroup_Toolset_Apr17_DS_ParseLogs {
   meta:
      description = "Detects EquationGroup Tool - April Leak"
      author = "Florian Roth"
      reference = "https://steemit.com/shadowbrokers/@theshadowbrokers/lost-in-translation"
      date = "2017-04-15"
      hash1 = "0228691d63038b072cdbf50782990d505507757efbfa87655bb2182cf6375956"
   strings:
      $x1 = "* Size (%d) of remaining capture file is too small to contain a valid header" fullword wide
      $x2 = "* Capture header not found at start of buffer" fullword wide
      $x3 = "Usage: %ws <capture_file> <results_prefix>" fullword wide
   condition:
      ( uint16(0) == 0x5a4d and filesize < 100KB and 1 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