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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_MAL_DLL_Stealer_Nov23

Detects a DLL that steals authentication credentials - was seen being used by LockBit 3.0 affiliates exploiting CVE-2023-4966

MalwareLockbitSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
X__Junior
Date
2023-11-23
Modified
2023-12-05
Score / Quality
80 / 85

What this rule detects

Detects a DLL that steals authentication credentials - was seen being used by LockBit 3.0 affiliates exploiting CVE-2023-4966

Associated malware family: Lockbit.

Targets: Windows PE.

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

Summary generated from the rule's metadata and condition.

Rule source

mal-dll-stealer-nov23.yarDetection Rule License 1.1
rule SIGNATURE_BASE_MAL_DLL_Stealer_Nov23 : CVE_2023_4966 FILE
{
	meta:
		description = "Detects a DLL that steals authentication credentials - was seen being used by LockBit 3.0 affiliates exploiting CVE-2023-4966"
		author = "X__Junior"
		id = "9cfed8ec-1d04-53d7-88ef-2576075cfc33"
		date = "2023-11-23"
		modified = "2023-12-05"
		reference = "https://www.cisa.gov/news-events/cybersecurity-advisories/aa23-325a"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/apt_ransom_lockbit_citrixbleed_nov23.yar#L41-L54"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "17a27b1759f10d1f6f1f51a11c0efea550e2075c2c394259af4d3f855bbcc994"
		logic_hash = "7d0c46d855973cb2c0636aed9c67cfbe47ca260ab1bc842fef1d532725c26910"
		score = 80
		quality = 85
		tags = "CVE-2023-4966, FILE"

	strings:
		$op1 = { C7 45 ?? 4D 69 6E 69 C7 45 ?? 44 75 6D 70 C7 45 ?? 57 72 69 74 C7 45 ?? 65 44 75 6D C7 45 ?? 70 00 27 00 C7 45 ?? 44 00 62 00 C7 45 ?? 67 00 68 00 C7 45 ?? 65 00 6C 00 C7 45 ?? 70 00 2E 00 C7 45 ?? 64 00 6C 00 C7 45 ?? 6C 00 00 00}

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

Strings (1 patterns)

IdentifierTypeValueModifiers
$op1hex{ C7 45 ?? 4D 69 6E 69 C7 45 ?? 44 75 6D 70 C7 45 ?? 57 72 69 74 C7 45 ?? 65 44 75 6D C7 45 ?? 70 00 27 00 C7 45 ?? 44 00 62 00 C7 45 ?? 67 00 68 00 C7 45 ?? 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

Sample hashes

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

  • 17a27b1759f10d1f6f1f51a11c0efea550e2075c2c394259af4d3f855bbcc994

Licence & attribution

Author: X__Junior

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: 9cfed8ec-1d04-53d7-88ef-2576075cfc33

Tags:CVE_2023_4966FILE

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