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Sednit / EVILTOSS Implant by APT28

yara CRITICAL Yara-Rules
aptcommunity
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: 2026-05-25T23:00:00Z · Confidence: medium

Hunt Hypothesis

The detection identifies potential deployment of the Sednit / EVILTOSS implant by APT28, indicating adversarial persistence and command-and-control capabilities. SOC teams should proactively hunt for this behavior to detect early-stage APT28 activity and prevent further compromise within their Azure Sentinel environment.

YARA Rule

rule IMPLANT_6_v4 {
   meta:
      description = "Sednit / EVILTOSS Implant by APT28"
      author = "US CERT"
      reference = "https://www.us-cert.gov/ncas/current-activity/2017/02/10/Enhanced-Analysis-GRIZZLY-STEPPE"
      date = "2017-02-10"
      score = 85
   strings:
      $ASM = {53 5? 5? [6-15] ff d? 8b ?? b? a0 86 01 00 [7-13] ff d? ?b
         [6-10] c0 [0-1] c3}
   condition:
   (uint16(0) == 0x5A4D or uint16(0) == 0xCFD0 or uint16(0) == 0xC3D4 or
   uint32(0) == 0x46445025 or uint32(1) == 0x6674725C) and all of them
}

Deployment Notes

This YARA rule can be deployed in the following contexts:

This rule contains 1 string patterns in its detection logic.

References

False Positive Guidance

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