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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_MAL_CRIME_Unknown_ISO_Jun21_1

Triggers on ISO files that mimick NOBELIUM TTPs, but uses LNK files that call powershell instead.

MalwareSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Nils Kuhnert
Date
2021-06-04
Modified
2023-12-05
Score / Quality
75 / 85

What this rule detects

Triggers on ISO files that mimick NOBELIUM TTPs, but uses LNK files that call powershell instead.

It defines 2 patterns (2 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
mal-crime-unknown-iso-jun21-1.yarDetection Rule License 1.1
rule SIGNATURE_BASE_MAL_CRIME_Unknown_ISO_Jun21_1 : ISO POWERSHELL LNK FILE
{
	meta:
		description = "Triggers on ISO files that mimick NOBELIUM TTPs, but uses LNK files that call powershell instead."
		author = "Nils Kuhnert"
		id = "73a1fc44-45c4-5253-b81d-fa6686dc0644"
		date = "2021-06-04"
		modified = "2023-12-05"
		reference = "https://github.com/Neo23x0/signature-base"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/mal_crime_unknown.yar#L35-L50"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "425dbed047dd2ce760d0848ebf7ad04b1ca360f111d557fc7bf657ae89f86d36"
		hash = "f6944b6bca627e219d9c5065f214f95eb2226897a3b823b645d0fd78c281b149"
		hash = "14d70a8bdd64e9a936c2dc9caa6d4506794505e0e3870e3a25d9d59bcafb046e"
		hash = "9b2ca8eb6db34b07647a74171a5ff4c0a2ca8000da9876ed2db6361958c5c080"
		logic_hash = "49b61f498d3f4ee249d9687277e581a39e08ebb4e1a293170058fb5f770bde1f"
		score = 75
		quality = 85
		tags = "ISO, POWERSHELL, LNK, FILE"

	strings:
		$uid = "S-1-5-21-1437133880-1006698037-385855442-1004" wide
		$magic = "CD001" ascii

	condition:
		filesize < 5MB and all of them
}

Strings (2 patterns)

IdentifierTypeValueModifiers
$uidtext"S-1-5-21-1437133880-1006698037-385855442-1004"wide
$magictext"CD001"ascii

Condition

filesize < 5MB and all of them

In plain words (Heuristic)

  • The file must be smaller than 5MB (a cheap guard that skips large files).
  • All patterns in the rule must match.

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References

Sample hashes

Hashes of samples the author lists in the rule's meta (look them up in your threat-intelligence platform).

  • 425dbed047dd2ce760d0848ebf7ad04b1ca360f111d557fc7bf657ae89f86d36
  • f6944b6bca627e219d9c5065f214f95eb2226897a3b823b645d0fd78c281b149
  • 14d70a8bdd64e9a936c2dc9caa6d4506794505e0e3870e3a25d9d59bcafb046e
  • 9b2ca8eb6db34b07647a74171a5ff4c0a2ca8000da9876ed2db6361958c5c080

Licence & attribution

Author: Nils Kuhnert

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: 73a1fc44-45c4-5253-b81d-fa6686dc0644

Tags:ISOPOWERSHELLLNKFILE

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