YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_APT_MAL_CISA_10365227_02_Clientuploader_Dec21

Detects ClientUploader_mqsvn

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

Author: CISA Code & Media Analysis
Date: 2021-12-23
Modified: 2021-12-24
Score / Quality: 80 / 81

What this rule detects

Detects ClientUploader_mqsvn

Targets: Windows PE.

It defines 6 patterns (4 text, 2 hex, 0 regex).

YARA-X says: warning[text_as_hex]: hex pattern could be written as text literal

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

apt-mal-cisa-10365227-02-clientuploader-dec21.yarDetection Rule License 1.1

rule SIGNATURE_BASE_APT_MAL_CISA_10365227_02_Clientuploader_Dec21 : FILE
{
	meta:
		description = "Detects ClientUploader_mqsvn"
		author = "CISA Code & Media Analysis"
		id = "84351df9-e225-5c3f-9385-523246681a97"
		date = "2021-12-23"
		modified = "2021-12-24"
		reference = "https://www.cisa.gov/uscert/ncas/analysis-reports/ar22-277a"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/apt_stealer_cisa_ar22_277a.yar#L48-L67"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "3585c3136686d7d48e53c21be61bb2908d131cf81b826acf578b67bb9d8e9350"
		logic_hash = "f9f82b4577568d0bd60bac0d3132ed7ffcb338f508a8689f3126f3d2440432ef"
		score = 80
		quality = 81
		tags = "FILE"

	strings:
		$s1 = "UploadSmallFileWithStopWatch"
		$s2 = "UploadPartWithStopwatch"
		$s3 = "AppVClient"
		$s4 = "ClientUploader"
		$s5 = { 46 69 6C 65 43 6F 6E 74 61 69 6E 65 72 2E 46 69 6C 65 41 72 63 68 69 76 65 }
		$s6 = { 4F 6E 65 44 72 69 76 65 43 6C 69 65 6E 74 2E 4F 6E 65 44 72 69 76 65 }

	condition:
		uint16( 0 ) == 0x5a4d and all of them
}

Strings (6 patterns)

Identifier	Type	Value
$s1	text	"UploadSmallFileWithStopWatch"
$s2	text	"UploadPartWithStopwatch"
$s3	text	"AppVClient"
$s4	text	"ClientUploader"
$s5	hex	{ 46 69 6C 65 43 6F 6E 74 61 69 6E 65 72 2E 46 69 6C 65 41 72 63 68 69 76 65 }
$s6	hex	{ 4F 6E 65 44 72 69 76 65 43 6C 69 65 6E 74 2E 4F 6E 65 44 72 69 76 65 }

Condition

uint16( 0 ) == 0x5a4d and all of them

In plain words (Heuristic)

The file must start with “MZ” — a Windows executable (PE).
All patterns in the rule must match.

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References

https://www.cisa.gov/uscert/ncas/analysis-reports/ar22-277a

Sample hashes

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

3585c3136686d7d48e53c21be61bb2908d131cf81b826acf578b67bb9d8e9350

Licence & attribution

Author: CISA Code & Media Analysis

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: 84351df9-e225-5c3f-9385-523246681a97

Tags:FILE

SIGNATURE_BASE_APT_MAL_CISA_10365227_01_APPSTORAGE_Dec21
APT / threat actorSignature Base (Florian Roth / Nextron)· CISA Code & Media Analysis· 2021-12-23
SIGNATURE_BASE_APT_MAL_CISA_10365227_03_Clientuploader_Dec21
APT / threat actorSignature Base (Florian Roth / Nextron)· CISA Code & Media Analysis· 2021-12-23