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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_APT_APT29_NOBELIUM_JS_Envyscout_May21_2

Detects EnvyScout deobfuscator code as used by NOBELIUM group

APT / threat actorSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Florian Roth (Nextron Systems)
Date
2021-05-29
Modified
2025-03-21
Score / Quality
75 / 85

What this rule detects

Detects EnvyScout deobfuscator code as used by NOBELIUM group

It defines 4 patterns (4 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
apt-apt29-nobelium-js-envyscout-may21-2.yarDetection Rule License 1.1
rule SIGNATURE_BASE_APT_APT29_NOBELIUM_JS_Envyscout_May21_2 : FILE
{
	meta:
		description = "Detects EnvyScout deobfuscator code as used by NOBELIUM group"
		author = "Florian Roth (Nextron Systems)"
		id = "d5cf3365-fe24-533a-a678-b5b6d4d99997"
		date = "2021-05-29"
		modified = "2025-03-21"
		reference = "https://www.microsoft.com/security/blog/2021/05/28/breaking-down-nobeliums-latest-early-stage-toolset/"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/apt_apt29_nobelium_may21.yar#L69-L83"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		logic_hash = "6f5c50b340d628559799897a2ba79add7d126e3ecb2daeb365bc15d64796ccd2"
		score = 75
		quality = 85
		tags = "FILE"

	strings:
		$s1 = "saveAs(blob, " ascii
		$s2 = ".iso\");" ascii
		$s3 = "application/x-cd-image" ascii
		$s4 = ".indexOf(\"Win\")!=-1" ascii

	condition:
		filesize < 5000KB and all of them
}

Strings (4 patterns)

IdentifierTypeValueModifiers
$s1text"saveAs(blob, "ascii
$s2text".iso\");"ascii
$s3text"application/x-cd-image"ascii
$s4text".indexOf(\"Win\")!=-1"ascii

Condition

filesize < 5000KB and all of them

In plain words (Heuristic)

  • The file must be smaller than 5000KB (a cheap guard that skips large files).
  • All patterns in the rule must match.

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References

Licence & attribution

Author: Florian Roth (Nextron Systems)

Source repository: Signature Base (Florian Roth / Nextron) @ 94a1c48d7a

Licence: Detection Rule License 1.1 (repository licence)

Original rule

Mirrored via YARA Forge 20260927, which prefixes rule names with the source and adds normalised meta fields.

Rule id: d5cf3365-fe24-533a-a678-b5b6d4d99997

Tags:FILE

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