YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_APT_MAL_Maldoc_Cloudatlas_Oct20_1

Detects unknown maldoc dropper noticed in October 2020

APT / threat actorSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X

Author: Florian Roth (Nextron Systems)
Date: 2020-10-13
Modified: 2023-12-05
Score / Quality: 75 / 85

What this rule detects

Detects unknown maldoc dropper noticed in October 2020

It defines 1 patterns (1 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

apt-mal-maldoc-cloudatlas-oct20-1.yarDetection Rule License 1.1

rule SIGNATURE_BASE_APT_MAL_Maldoc_Cloudatlas_Oct20_1 : FILE
{
	meta:
		description = "Detects unknown maldoc dropper noticed in October 2020"
		author = "Florian Roth (Nextron Systems)"
		id = "e7caf2b2-caf2-5984-a792-8224f2641bda"
		date = "2020-10-13"
		modified = "2023-12-05"
		reference = "https://twitter.com/jfslowik/status/1316050637092651009"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/apt_cloudatlas.yar#L2-L16"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "7ba76b2311736dbcd4f2817c40dae78f223366f2404571cd16d6676c7a640d70"
		logic_hash = "772bdd8ec89edf2054e675e9ecb321a7bfe0307a7086a4e5b65f8d8b8cf80ecc"
		score = 75
		quality = 85
		tags = "FILE"

	strings:
		$x1 = "https://msofficeupdate.org" wide

	condition:
		uint16( 0 ) == 0xcfd0 and filesize < 300KB and 1 of ( $x* )
}

Strings (1 patterns)

Identifier	Type	Value	Modifiers
$x1	text	"https://msofficeupdate.org"	wide

Condition

uint16( 0 ) == 0xcfd0 and filesize < 300KB and 1 of ( $x* )

In plain words (Heuristic)

The file must be smaller than 300KB (a cheap guard that skips large files).
At least 1 patterns in ( $x* ) must match.

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References

https://twitter.com/jfslowik/status/1316050637092651009

Sample hashes

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

7ba76b2311736dbcd4f2817c40dae78f223366f2404571cd16d6676c7a640d70

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: e7caf2b2-caf2-5984-a792-8224f2641bda

Tags:FILE

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