YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_APT_MAL_Revil_Kaseya_Jul21_2

Detects malware used in the Kaseya supply chain attack

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

Author: Florian Roth (Nextron Systems)
Date: 2021-07-02
Modified: 2023-12-05
Score / Quality: 75 / 85

What this rule detects

Detects malware used in the Kaseya supply chain attack

Associated malware family: Revil.

Targets: Windows PE.

It defines 7 patterns (0 text, 7 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

apt-mal-revil-kaseya-jul21-2.yarDetection Rule License 1.1

rule SIGNATURE_BASE_APT_MAL_Revil_Kaseya_Jul21_2 : FILE
{
	meta:
		description = "Detects malware used in the Kaseya supply chain attack"
		author = "Florian Roth (Nextron Systems)"
		id = "38b168d4-e761-544e-9859-eb155bbfe54a"
		date = "2021-07-02"
		modified = "2023-12-05"
		reference = "https://doublepulsar.com/kaseya-supply-chain-attack-delivers-mass-ransomware-event-to-us-companies-76e4ec6ec64b"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/crime_revil_general.yar#L32-L57"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "0496ca57e387b10dfdac809de8a4e039f68e8d66535d5d19ec76d39f7d0a4402"
		hash = "8dd620d9aeb35960bb766458c8890ede987c33d239cf730f93fe49d90ae759dd"
		hash = "cc0cdc6a3d843e22c98170713abf1d6ae06e8b5e34ed06ac3159adafe85e3bd6"
		hash = "d5ce6f36a06b0dc8ce8e7e2c9a53e66094c2adfc93cfac61dd09efe9ac45a75f"
		hash = "d8353cfc5e696d3ae402c7c70565c1e7f31e49bcf74a6e12e5ab044f306b4b20"
		hash = "e2a24ab94f865caeacdf2c3ad015f31f23008ac6db8312c2cbfb32e4a5466ea2"
		logic_hash = "44948d93c71370a9976f22bf78cd1af80359f2c9804ea7995791109785cfaf84"
		score = 75
		quality = 85
		tags = "FILE"

	strings:
		$opa1 = { 8b 4d fc 83 c1 01 89 4d fc 81 7d f0 ff 00 00 00 77 1? ba 01 00 00 00 6b c2 00 8b 4d 08 }
		$opa2 = { 89 45 f0 8b 4d fc 83 c1 01 89 4d fc 81 7d f0 ff 00 00 00 77 1? ba 01 00 00 00 6b c2 00 }
		$opa3 = { 83 c1 01 89 4d fc 81 7d f0 ff 00 00 00 77 1? ba 01 00 00 00 6b c2 00 8b 4d 08 0f b6 14 01 }
		$opa4 = { 89 45 f4 8b 0d ?? ?0 07 10 89 4d f8 8b 15 ?? ?1 07 10 89 55 fc ff 75 fc ff 75 f8 ff 55 f4 }
		$opb1 = { 18 00 10 bd 18 00 10 bd 18 00 10 0e 19 00 10 cc cc cc }
		$opb2 = { 18 00 10 0e 19 00 10 cc cc cc cc 8b 44 24 04 }
		$opb3 = { 10 c4 18 00 10 bd 18 00 10 bd 18 00 10 0e 19 00 10 cc cc }

	condition:
		uint16( 0 ) == 0x5a4d and filesize < 3000KB and ( 2 of ( $opa* ) or 3 of them )
}

Strings (7 patterns)

Identifier	Type	Value
$opa1	hex	{ 8b 4d fc 83 c1 01 89 4d fc 81 7d f0 ff 00 00 00 77 1? ba 01 00 00 00 6b c2 00 8b 4d 08 }
$opa2	hex	{ 89 45 f0 8b 4d fc 83 c1 01 89 4d fc 81 7d f0 ff 00 00 00 77 1? ba 01 00 00 00 6b c2 00 }
$opa3	hex	{ 83 c1 01 89 4d fc 81 7d f0 ff 00 00 00 77 1? ba 01 00 00 00 6b c2 00 8b 4d 08 0f b6 14 01 }
$opa4	hex	{ 89 45 f4 8b 0d ?? ?0 07 10 89 4d f8 8b 15 ?? ?1 07 10 89 55 fc ff 75 fc ff 75 f8 ff 55 f4 }
$opb1	hex	{ 18 00 10 bd 18 00 10 bd 18 00 10 0e 19 00 10 cc cc cc }
$opb2	hex	{ 18 00 10 0e 19 00 10 cc cc cc cc 8b 44 24 04 }
$opb3	hex	{ 10 c4 18 00 10 bd 18 00 10 bd 18 00 10 0e 19 00 10 cc cc }

Condition

uint16( 0 ) == 0x5a4d and filesize < 3000KB and ( 2 of ( $opa* ) or 3 of them )

In plain words (Heuristic)

The file must start with “MZ” — a Windows executable (PE).
The file must be smaller than 3000KB (a cheap guard that skips large files).
At least 2 patterns in ( $opa* ) must match.
At least 3 patterns in the rule must match.

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References

https://doublepulsar.com/kaseya-supply-chain-attack-delivers-mass-ransomware-event-to-us-companies-76e4ec6ec64b

Sample hashes

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

0496ca57e387b10dfdac809de8a4e039f68e8d66535d5d19ec76d39f7d0a4402
8dd620d9aeb35960bb766458c8890ede987c33d239cf730f93fe49d90ae759dd
cc0cdc6a3d843e22c98170713abf1d6ae06e8b5e34ed06ac3159adafe85e3bd6
d5ce6f36a06b0dc8ce8e7e2c9a53e66094c2adfc93cfac61dd09efe9ac45a75f
d8353cfc5e696d3ae402c7c70565c1e7f31e49bcf74a6e12e5ab044f306b4b20
e2a24ab94f865caeacdf2c3ad015f31f23008ac6db8312c2cbfb32e4a5466ea2

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: 38b168d4-e761-544e-9859-eb155bbfe54a

Tags:FILE

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