YARA · ESET malware-ioc

ESET_Apt_Windows_TA410_Flowcloud_Header_Decryption

Matches the function used to decrypt resources headers in TA410 FlowCloud

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

Author: ESET Research
Date: 2026-01-27
Modified: 2022-04-27
Score / Quality: 75 / 80

What this rule detects

Matches the function used to decrypt resources headers in TA410 FlowCloud

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-header-decryption.yarBSD 2-Clause License

rule ESET_Apt_Windows_TA410_Flowcloud_Header_Decryption : FILE
{
	meta:
		description = "Matches the function used to decrypt resources headers in TA410 FlowCloud"
		author = "ESET Research"
		id = "403c1845-bc25-5a49-8553-8a0be18d6970"
		date = "2026-01-27"
		modified = "2022-04-27"
		reference = "https://github.com/eset/malware-ioc/"
		source_url = "https://github.com/eset/malware-ioc/blob/17baf44964a77368e9149f4f593eb098beddf1c5/ta410/ta410.yar#L417-L496"
		license_url = "https://github.com/eset/malware-ioc/blob/17baf44964a77368e9149f4f593eb098beddf1c5/LICENSE"
		logic_hash = "74b6c42bf2de159b2b0a15637e6bd94069367e3000c887714d6e3b50aa3646be"
		score = 75
		quality = 80
		tags = "FILE"
		license = "BSD 2-Clause"

	strings:
		$chunk_1 = {
            8B 1E
            8B CF
            D3 CB
            8D 0C 28
            83 C7 06
            30 18
            8B 1E
            D3 CB
            8D 0C 02
            30 58 ??
            8B 1E
            D3 CB
            8B 4C 24 ??
            03 C8
            30 58 ??
            8B 1E
            D3 CB
            8B 4C 24 ??
            03 C8
            30 58 ??
            8B 1E
            D3 CB
            8B 4C 24 ??
            03 C8
            83 C0 06
            30 58 ??
            8B 1E
            D3 CB
            30 58 ??
            83 FF 10
            72 ??
        }

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

Strings (1 patterns)

Identifier	Type	Value	Modifiers
$chunk_1	hex	{ 8B 1E 8B CF D3 CB 8D 0C 28 83 C7 06 30 18 8B 1E D3 CB …

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: 403c1845-bc25-5a49-8553-8a0be18d6970

Tags:FILE

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