YARA · SEKOIA.IO Community

SEKOIA_Apt_3Cx_Payload_Stealer

Detects stealer used in 3CX campaign

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

Author: Sekoia.io
Date: 2023-03-31
Modified: 2024-12-19
Score / Quality: 75 / 80

What this rule detects

Detects stealer used in 3CX campaign

Targets: Windows PE, Linux ELF.

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

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

apt-3cx-payload-stealer.yarDetection Rule License 1.1

rule SEKOIA_Apt_3Cx_Payload_Stealer : FILE
{
	meta:
		description = "Detects stealer used in 3CX campaign"
		author = "Sekoia.io"
		id = "1ca0605d-101f-4d1d-a476-9dfd93e74b4c"
		date = "2023-03-31"
		modified = "2024-12-19"
		reference = "https://github.com/SEKOIA-IO/Community"
		source_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/yara_rules/apt_3cx_payload_stealer.yar#L1-L20"
		license_url = "https://github.com/SEKOIA-IO/Community/blob/a438a5901a211c2abdf75da9c93921ef187473d1/LICENSE.md"
		logic_hash = "17630ab86a3da3408e29765c0c30f14c76b870b88fea634b998392fe5d46cfa2"
		score = 75
		quality = 80
		tags = "FILE"
		version = "1.0"
		classification = "TLP:CLEAR"

	strings:
		$s1 = "******************************** %s ******************************" wide
		$s2 = "\\3CXDesktopApp\\config.json" wide
		$s3 = "{\"HostName\": \"%s\", \"DomainName\": \"%s\", \"OsVersion\":" wide
		$s4 = "%s.old" wide

	condition:
		( uint32be( 0 ) == 0x7f454c46 or uint16be( 0 ) == 0x4d5a ) and filesize < 8MB and all of them
}

Strings (4 patterns)

Identifier	Type	Value	Modifiers
$s1	text	"****************************** %s ****************************"	wide
$s2	text	"\\3CXDesktopApp\\config.json"	wide
$s3	text	"{\"HostName\": \"%s\", \"DomainName\": \"%s\", \"OsVersion\":"	wide
$s4	text	"%s.old"	wide

Condition

( uint32be( 0 ) == 0x7f454c46 or uint16be( 0 ) == 0x4d5a ) and filesize < 8MB 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 8MB (a cheap guard that skips large files).
All patterns in the rule must match.

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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: 1ca0605d-101f-4d1d-a476-9dfd93e74b4c

Metadata

version	1.0
classification	TLP:CLEAR

Tags:FILE

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