YARA · SEKOIA.IO Community

SEKOIA_Apt_Mustangpanda_Coolclient

Detect COOLCLIENT via obfuscation & specific string

APT / threat actorSEKOIA.IO CommunityDetection Rule License 1.1Compiles with YARA-X

Author: Sekoia.io
Date: 2023-03-27
Modified: 2024-12-19
Score / Quality: 75 / 80

What this rule detects

Detect COOLCLIENT via obfuscation & specific string

Targets: Windows PE, Linux ELF.

It defines 3 patterns (1 text, 2 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

apt-mustangpanda-coolclient.yarDetection Rule License 1.1

rule SEKOIA_Apt_Mustangpanda_Coolclient : FILE
{
	meta:
		description = "Detect COOLCLIENT via obfuscation & specific string"
		author = "Sekoia.io"
		id = "2f8fdb66-03a2-400f-808b-56ae1b276d2f"
		date = "2023-03-27"
		modified = "2024-12-19"
		reference = "https://github.com/SEKOIA-IO/Community"
		source_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/apt_mustangpanda_coolclient.yar#L1-L19"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		logic_hash = "9fd552604299ecb8fa28042ee26e72bbe4fb9804ad087bf4a373b2c2e17d43b0"
		score = 75
		quality = 80
		tags = "FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$s1 = {eb 14 ea 50 eb 0b ea 8b c4 a8 01 74 06 eb 0b}
		$s2 = {66 0f d6 44 24 eb eb}
		$s3 = "c:\\windows\\syste" fullword

	condition:
		( uint32be( 0 ) == 0x7f454c46 or uint16be( 0 ) == 0x4d5a ) and filesize < 1MB and all of them
}

Strings (3 patterns)

Identifier	Type	Value	Modifiers
$s1	hex	{eb 14 ea 50 eb 0b ea 8b c4 a8 01 74 06 eb 0b}
$s2	hex	{66 0f d6 44 24 eb eb}
$s3	text	"c:\\windows\\syste"	fullword

Condition

( uint32be( 0 ) == 0x7f454c46 or uint16be( 0 ) == 0x4d5a ) and filesize < 1MB and all of them

In plain words (Heuristic)

The file must start with “MZ” — a Windows executable (PE).
The file must start with the ELF header — a Linux/Unix executable.
The file must be smaller than 1MB (a cheap guard that skips large files).
All patterns in the rule must match.

Test this rule in your browser

Drop a file to scan it with this rule using YARA-X compiled to WebAssembly. Nothing is uploaded.

Drop a file here or click to chooseScanned locally with YARA-X. Files up to 200 MB.

Open in editor

References

https://github.com/SEKOIA-IO/Community

Licence & attribution

Author: Sekoia.io

Source repository: SEKOIA.IO Community @ a438a5901a

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: 2f8fdb66-03a2-400f-808b-56ae1b276d2f

Metadata

version	1.0
classification	TLP:CLEAR

Tags:FILE

SEKOIA_Apt_Gobrat_2
APT / threat actorSEKOIA.IO Community· Sekoia.io· 2024-09-10
SEKOIA_Apt_Icepeony_Icecache
APT / threat actorSEKOIA.IO Community· Sekoia.io· 2024-10-21
SEKOIA_Apt_Icepeony_Iceevent
APT / threat actorSEKOIA.IO Community· Sekoia.io· 2024-10-21
SEKOIA_Apt_Kimsuky_Fpspy
APT / threat actorSEKOIA.IO Community· Sekoia.io· 2024-09-27
SEKOIA_Apt_Kimsuky_Klogexe
APT / threat actorSEKOIA.IO Community· Sekoia.io· 2024-09-27
SEKOIA_Apt_Kimsuky_Powershell
APT / threat actorSEKOIA.IO Community· Sekoia.io· 2024-09-23
SEKOIA_Apt_Kimsuky_Powershell_Dropper_Strings
APT / threat actorSEKOIA.IO Community· Sekoia.io· 2024-06-11
SEKOIA_Apt_Kimsuky_Toddlershark_Obfuscated
APT / threat actorSEKOIA.IO Community· Sekoia.io· 2024-03-06