YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_SUSP_APT_MAL_NK_3CX_Malicious_Samples_Mar23_1

Detects marker found in malicious DLLs related to 3CX compromise

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

Author: X__Junior, Florian Roth (Nextron Systems)
Date: 2023-03-29
Modified: 2023-04-20
Score / Quality: 75 / 85

What this rule detects

Detects marker found in malicious DLLs related to 3CX compromise

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

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

susp-apt-mal-nk-3cx-malicious-samples-mar23-1.yarDetection Rule License 1.1

rule SIGNATURE_BASE_SUSP_APT_MAL_NK_3CX_Malicious_Samples_Mar23_1
{
	meta:
		description = "Detects marker found in malicious DLLs related to 3CX compromise"
		author = "X__Junior, Florian Roth (Nextron Systems)"
		id = "9fc6eb94-d02f-5bcd-9f55-b6c6a8301b4f"
		date = "2023-03-29"
		modified = "2023-04-20"
		reference = "https://www.reddit.com/r/crowdstrike/comments/125r3uu/20230329_situational_awareness_crowdstrike/"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/gen_mal_3cx_compromise_mar23.yar#L81-L98"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "7986bbaee8940da11ce089383521ab420c443ab7b15ed42aed91fd31ce833896"
		hash = "c485674ee63ec8d4e8fde9800788175a8b02d3f9416d0e763360fff7f8eb4e02"
		hash = "cc4eedb7b1f77f02b962f4b05278fa7f8082708b5a12cacf928118520762b5e2"
		logic_hash = "dcce1f5e769a2821d746a960cd333f8042fb71c8469aa41c29bbbd0dce79369c"
		score = 75
		quality = 85
		tags = ""

	strings:
		$opx1 = { 41 80 7C 00 FD FE 75 ?? 41 80 7C 00 FE ED 75 ?? 41 80 7C 00 FF FA 75 ?? 41 80 3C 00 CE }
		$opx2 = { 80 78 ?? FE 75 ?? 80 78 ?? ED 75 ?? 80 38 FA 75 ?? 80 78 ?? CE }

	condition:
		1 of them
}

Strings (2 patterns)

Identifier	Type	Value	Modifiers
$opx1	hex	{ 41 80 7C 00 FD FE 75 ?? 41 80 7C 00 FE ED 75 ?? 41 80 7C 00 FF FA 75 ?? 41 80 3C 00 CE }
$opx2	hex	{ 80 78 ?? FE 75 ?? 80 78 ?? ED 75 ?? 80 38 FA 75 ?? 80 78 ?? CE }

Condition

1 of them

In plain words (Heuristic)

At least 1 patterns in the rule must match.

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References

https://www.reddit.com/r/crowdstrike/comments/125r3uu/20230329_situational_awareness_crowdstrike/

Sample hashes

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

7986bbaee8940da11ce089383521ab420c443ab7b15ed42aed91fd31ce833896
c485674ee63ec8d4e8fde9800788175a8b02d3f9416d0e763360fff7f8eb4e02
cc4eedb7b1f77f02b962f4b05278fa7f8082708b5a12cacf928118520762b5e2

Licence & attribution

Author: X__Junior, 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: 9fc6eb94-d02f-5bcd-9f55-b6c6a8301b4f

SIGNATURE_BASE_APT_MAL_NK_3CX_Malicious_Samples_Mar23_1
APT / threat actorSignature Base (Florian Roth / Nextron)· X__Junior, Florian Roth (Nextron Systems)· 2023-03-29