YARA · ESET malware-ioc

ESET_Apt_Windows_TA410_Flowcloud_Shellcode_Decryption

Matches the decryption function used in TA410 FlowCloud self-decrypting DLL

APT / threat actorESET malware-iocBSD 2-Clause LicenseCompiles with YARA-X

Author: ESET Research
Date: 2021-10-12
Modified: 2022-04-27
Score / Quality: 75 / 80

What this rule detects

Matches the decryption function used in TA410 FlowCloud self-decrypting DLL

Targets: Windows PE.

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

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

apt-windows-ta410-flowcloud-shellcode-decryption.yarBSD 2-Clause License

rule ESET_Apt_Windows_TA410_Flowcloud_Shellcode_Decryption : FILE
{
	meta:
		description = "Matches the decryption function used in TA410 FlowCloud self-decrypting DLL"
		author = "ESET Research"
		id = "8af7b2fa-be40-5ec8-8413-1c982a463a9a"
		date = "2021-10-12"
		modified = "2022-04-27"
		reference = "https://github.com/eset/malware-ioc/"
		source_url = "https://github.com/eset/malware-ioc/blob/17baf44964a77368e9149f4f593eb098beddf1c5/ta410/ta410.yar#L569-L615"
		license_url = "https://github.com/eset/malware-ioc/blob/17baf44964a77368e9149f4f593eb098beddf1c5/LICENSE"
		logic_hash = "939ffe6a41c957aa5d6c012484b2deab49a5e71a4b7e203a41c180f872803921"
		score = 75
		quality = 80
		tags = "FILE"
		license = "BSD 2-Clause"
		version = "1"

	strings:
		$chunk_1 = {
            33 D2
            8B 45 ??
            BB 6B 04 00 00
            F7 F3
            81 C2 A8 01 00 00
            81 E2 FF 00 00 00
            8B 7D ??
            33 C9
            EB ??
            30 14 39
            00 14 39
            41
            3B 4D ??
            72 ??
        }

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

Strings (1 patterns)

Identifier	Type	Value	Modifiers
$chunk_1	hex	{ 33 D2 8B 45 ?? BB 6B 04 00 00 F7 F3 81 C2 A8 01 00 00 81 E2 FF 00 00 00 8B …

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

https://github.com/eset/malware-ioc/

Licence & attribution

Author: ESET Research

Source repository: ESET malware-ioc @ 17baf44964

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

“BSD 2-Clause”

Original rule

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

Rule id: 8af7b2fa-be40-5ec8-8413-1c982a463a9a

Metadata

version	1

Tags:FILE

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