YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_MAL_Katz_Stealer_May25

Detects Katz stealer

MalwareKatz StealerSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X

Author: MalGamy (Nextron Systems)
Date: 2025-05-16
Modified: 2026-05-15
Score / Quality: 80 / 85

What this rule detects

Detects Katz stealer

Associated malware family: Katz Stealer.

Targets: Windows PE.

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

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

mal-katz-stealer-may25.yarDetection Rule License 1.1

rule SIGNATURE_BASE_MAL_Katz_Stealer_May25 : FILE
{
	meta:
		description = "Detects Katz stealer"
		author = "MalGamy (Nextron Systems)"
		id = "ef84df99-3c1a-56b6-a0fd-39876982d0c3"
		date = "2025-05-16"
		modified = "2026-05-15"
		reference = "Internal Research"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/mal_katz_stealer.yar#L1-L22"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "fdc86a5b3d7df37a72c3272836f743747c47bfbc538f05af9ecf78547fa2e789"
		hash = "d92bb6e47cb0a0bdbb51403528ccfe643a9329476af53b5a729f04a4d2139647"
		logic_hash = "73364c2291dc792f46858dda057f08805db55fe1f1e54d6b0dee0a0c8a412259"
		score = 80
		quality = 85
		tags = "FILE"

	strings:
		$s1 = "Motherboard Product: %s" ascii
		$s2 = "cmd.exe /c %s" ascii
		$s3 = "reg export \"%s\" \"%s\" /y" ascii
		$s4 = ").request({ hostname: '" ascii
		$s5 = "Type: Removable"
		$s6 = "%s\\Microsoft\\Windows Live Mail" ascii

	condition:
		uint16( 0 ) == 0x5a4d and filesize < 300KB and 4 of them
}

Strings (6 patterns)

Identifier	Type	Value	Modifiers
$s1	text	"Motherboard Product: %s"	ascii
$s2	text	"cmd.exe /c %s"	ascii
$s3	text	"reg export \"%s\" \"%s\" /y"	ascii
$s4	text	").request({ hostname: '"	ascii
$s5	text	"Type: Removable"
$s6	text	"%s\\Microsoft\\Windows Live Mail"	ascii

Condition

uint16( 0 ) == 0x5a4d and filesize < 300KB and 4 of them

In plain words (Heuristic)

The file must start with “MZ” — a Windows executable (PE).
The file must be smaller than 300KB (a cheap guard that skips large files).
At least 4 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

Sample hashes

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

fdc86a5b3d7df37a72c3272836f743747c47bfbc538f05af9ecf78547fa2e789
d92bb6e47cb0a0bdbb51403528ccfe643a9329476af53b5a729f04a4d2139647

Licence & attribution

Author: MalGamy (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: ef84df99-3c1a-56b6-a0fd-39876982d0c3

Tags:FILE

SIGNATURE_BASE_MAL_NET_Katz_Stealer_Loader_May25
MalwareSignature Base (Florian Roth / Nextron)· Jonathan Peters (cod3nym)· 2025-05-21
MALPEDIA_Win_Katz_Stealer_Auto
MalwareMalpedia signator rules· Felix Bilstein - yara-signator at cocacoding dot com· 2026-05-04
SIGNATURE_BASE_APT_MAL_NK_3CX_Malicious_Samples_Mar23_4
APT / threat actorSignature Base (Florian Roth / Nextron)· MalGamy (Nextron Systems)· 2023-03-29

More Katz Stealer rules