YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_MAL_RANSOM_Lorenz_May21_1

Detects Lorenz Ransomware samples

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

Author: Florian Roth (Nextron Systems)
Date: 2021-05-04
Modified: 2023-12-05
Score / Quality: 75 / 85

What this rule detects

Detects Lorenz Ransomware samples

Associated malware family: Lorenz.

Targets: Windows PE.

It defines 7 patterns (5 text, 2 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

mal-ransom-lorenz-may21-1.yarDetection Rule License 1.1

rule SIGNATURE_BASE_MAL_RANSOM_Lorenz_May21_1 : FILE
{
	meta:
		description = "Detects Lorenz Ransomware samples"
		author = "Florian Roth (Nextron Systems)"
		id = "0b18a4a3-82da-574b-8d10-daf2176448b9"
		date = "2021-05-04"
		modified = "2023-12-05"
		reference = "Internal Research - DACH TE"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/mal_ransom_lorenz.yar#L1-L28"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "4b1170f7774acfdc5517fbe1c911f2bd9f1af498f3c3d25078f05c95701cc999"
		hash = "8258c53a44012f6911281a6331c3ecbd834b6698b7d2dbf4b1828540793340d1"
		hash = "c0c99b141b014c8e2a5c586586ae9dc01fd634ea977e2714fbef62d7626eb3fb"
		logic_hash = "aec940deb2c3bc099a50a2e8f014ae425d306d331078d9ac2abc2ec7b8bf572e"
		score = 75
		quality = 85
		tags = "FILE"

	strings:
		$x1 = "process call create \"cmd.exe /c schtasks /Create /F /RU System /SC ONLOGON " ascii fullword
		$x2 = "-----BEGIN PUBLIC KEY-----MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCn7fL/1qsWkJkUtXKZIJNqYfnVByVhK" ascii fullword
		$s1 = "process call create \"cmd.exe /c schtasks /Create /F " ascii fullword
		$s2 = "twr.ini" ascii fullword
		$s3 = "/c wmic /node:'" ascii fullword
		$op1 = { 0f 4f d9 81 ff dc 0f 00 00 5f 8d 4b 0? 0f 4e cb 83 fe 3c 5e 5b }
		$op2 = { 6a 02 e8 ?? ?? 0? 00 83 c4 18 83 f8 01 75 01 cc 6a 00 68 ?? ?? 00 00 }

	condition:
		uint16( 0 ) == 0x5a4d and filesize < 4000KB and ( 1 of ( $x* ) or all of ( $op* ) or 3 of them )
}

Strings (7 patterns)

Identifier	Type	Value	Modifiers
$x1	text	"process call create \"cmd.exe /c schtasks /Create /F /RU System /SC ONLOGON "	ascii fullword
$x2	text	"-----BEGIN PUBLIC KEY-----MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgQCn7fL/1qsWkJkUtXKZIJNqYfnVByVhK"	ascii fullword
$s1	text	"process call create \"cmd.exe /c schtasks /Create /F "	ascii fullword
$s2	text	"twr.ini"	ascii fullword
$s3	text	"/c wmic /node:'"	ascii fullword
$op1	hex	{ 0f 4f d9 81 ff dc 0f 00 00 5f 8d 4b 0? 0f 4e cb 83 fe 3c 5e 5b }
$op2	hex	{ 6a 02 e8 ?? ?? 0? 00 83 c4 18 83 f8 01 75 01 cc 6a 00 68 ?? ?? 00 00 }

Condition

uint16( 0 ) == 0x5a4d and filesize < 4000KB and ( 1 of ( $x* ) or all of ( $op* ) or 3 of them )

In plain words (Heuristic)

The file must start with “MZ” — a Windows executable (PE).
The file must be smaller than 4000KB (a cheap guard that skips large files).
All patterns in ( $op* ) must match.
At least 1 patterns in ( $x* ) must match.
At least 3 patterns in the rule must match.

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Sample hashes

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

4b1170f7774acfdc5517fbe1c911f2bd9f1af498f3c3d25078f05c95701cc999
8258c53a44012f6911281a6331c3ecbd834b6698b7d2dbf4b1828540793340d1
c0c99b141b014c8e2a5c586586ae9dc01fd634ea977e2714fbef62d7626eb3fb

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: 0b18a4a3-82da-574b-8d10-daf2176448b9

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