YARA · Volexity threat-intel

VOLEXITY_Apt_Malware_Win_Decrok

The DECROK malware family, which uses the victim's hostname to decrypt and execute an embedded payload.

APT / threat actorVolexity threat-intelBSD 2-Clause LicenseCompiles with YARA-X

Author: threatintel@volexity.com
Date: 2021-06-23
Modified: 2023-09-28
Score / Quality: 75 / 80

What this rule detects

The DECROK malware family, which uses the victim's hostname to decrypt and execute an embedded payload.

It defines 5 patterns (4 text, 1 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

apt-malware-win-decrok.yarBSD 2-Clause License

rule VOLEXITY_Apt_Malware_Win_Decrok : INKYPINE FILE MEMORY
{
	meta:
		description = "The DECROK malware family, which uses the victim's hostname to decrypt and execute an embedded payload."
		author = "threatintel@volexity.com"
		id = "46be1793-6419-54fe-a78b-5d087e02626e"
		date = "2021-06-23"
		modified = "2023-09-28"
		reference = "https://github.com/volexity/threat-intel"
		source_url = "https://github.com/volexity/threat-intel/blob/3a9d0b52459877ee866a9a0ba06e60059b778c77/2021/2021-08-24 - InkySquid Part 2/indicators/yara.yar#L62-L90"
		license_url = "https://github.com/volexity/threat-intel/blob/3a9d0b52459877ee866a9a0ba06e60059b778c77/LICENSE.txt"
		hash = "6a452d088d60113f623b852f33f8f9acf0d4197af29781f889613fed38f57855"
		logic_hash = "a551700943d5abc95af00fc4fefd416ace8d59037852c6bc5caf1d6bd09afd63"
		score = 75
		quality = 80
		tags = "INKYPINE, FILE, MEMORY"
		os = "win"
		os_arch = "x86"
		scan_context = "file,memory"
		severity = "critical"
		license = "See license at https://github.com/volexity/threat-intel/blob/main/LICENSE.txt"
		rule_id = 5606
		version = 4

	strings:
		$v1 = {C7 ?? ?? ?? 01 23 45 67 [2-20] C7 ?? ?? ?? 89 AB CD EF C7 ?? ?? ?? FE DC BA 98}
		$av1 = "Select * From AntiVirusProduct" wide
		$av2 = "root\\SecurityCenter2" wide
		$func1 = "CreateThread"
		$format = "%02x"

	condition:
		all of them and $func1 in ( @format .. @format + 10 )
}

Strings (5 patterns)

Identifier	Type	Value	Modifiers
$v1	hex	{C7 ?? ?? ?? 01 23 45 67 [2-20] C7 ?? ?? ?? 89 AB CD EF C7 ?? ?? ?? FE DC BA 98}
$av1	text	"Select * From AntiVirusProduct"	wide
$av2	text	"root\\SecurityCenter2"	wide
$func1	text	"CreateThread"
$format	text	"%02x"

Condition

all of them and $func1 in ( @format .. @format + 10 )

In plain words (Heuristic)

All patterns in the rule must match.
Pattern $func1 must be found within the range @format .. @format + 10.

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References

https://github.com/volexity/threat-intel

Sample hashes

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

6a452d088d60113f623b852f33f8f9acf0d4197af29781f889613fed38f57855

Licence & attribution

Author: threatintel@volexity.com

Source repository: Volexity threat-intel @ 3a9d0b5245

Licence: BSD 2-Clause License (stated in the rule's own meta)

“See license at https://github.com/volexity/threat-intel/blob/main/LICENSE.txt”

Original rule

Mirrored via YARA Forge 20260927, which prefixes rule names with the source and adds normalised meta fields.

Rule id: 46be1793-6419-54fe-a78b-5d087e02626e

Metadata

os	win
os_arch	x86
scan_context	file,memory
severity	critical
rule_id	5606
version	4

Tags:INKYPINE FILE MEMORY

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