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YARA · CAPE Sandbox (CAPEv2)

CAPE_Formhelper

Formbook Config Extraction

MalwareFormbookCAPE Sandbox (CAPEv2)GNU General Public License v3.0Compiles with YARA-X
Author
kevoreilly
Date
2021-03-07
Modified
2026-05-15
Score / Quality
75 / 70

What this rule detects

Formbook Config Extraction

Associated malware family: Formbook.

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

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
formhelper.yarGNU General Public License v3.0
rule CAPE_Formhelper
{
	meta:
		description = "Formbook Config Extraction"
		author = "kevoreilly"
		id = "83b56e70-892e-5918-aff7-c2c41a89a5ab"
		date = "2021-03-07"
		modified = "2026-05-15"
		reference = "https://github.com/kevoreilly/CAPEv2"
		source_url = "https://github.com/kevoreilly/CAPEv2/blob/6b15e76f28cd83fd1187da6c9aaaad2174255356/analyzer/windows/data/yara/Formbook.yar#L46-L58"
		license_url = "https://github.com/kevoreilly/CAPEv2/blob/6b15e76f28cd83fd1187da6c9aaaad2174255356/LICENSE"
		logic_hash = "e049fba8e53934587f97bda5108cf9cece4169a8ff65a5d2788a98f709a68dc0"
		score = 75
		quality = 70
		tags = ""
		cape_options = "clear,bp2=$config,action2=scan,count=0"
		packed = "0270016f451f9ba630f2ea4e2ea006fb89356627835b560bb2f4551a735ba0e1"

	strings:
		$config = {40 55 53 56 57 41 54 41 55 41 56 41 57 48 8D AC 24 [4] 48 81 EC [2] 00 00 45 33 ?? 33 C0 4C 8B E9 4C 89}
		$decode = {66 66 66 66 0F 1F 84 00 00 00 00 00 0F (B6|B7) [2-5] 48 FF C9 ?? 41}

	condition:
		all of them
}

Strings (2 patterns)

IdentifierTypeValueModifiers
$confighex{40 55 53 56 57 41 54 41 55 41 56 41 57 48 8D AC 24 [4] 48 81 EC [2] 00 00 45 33 ?? 33 C0 4C 8B E9 4C 89}
$decodehex{66 66 66 66 0F 1F 84 00 00 00 00 00 0F (B6|B7) [2-5] 48 FF C9 ?? 41}

Condition

all of them

In plain words (Heuristic)

  • All patterns in the rule must match.

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References

Licence & attribution

Author: kevoreilly

Source repository: CAPE Sandbox (CAPEv2) @ 6b15e76f28

Licence: GNU General Public License v3.0 (repository licence)

Copyright notice: Cuckoo Sandbox is copyrighted by the Cuckoo Foundation.

Original rule

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

Rule id: 83b56e70-892e-5918-aff7-c2c41a89a5ab

Metadata

cape_optionsclear,bp2=$config,action2=scan,count=0
packed0270016f451f9ba630f2ea4e2ea006fb89356627835b560bb2f4551a735ba0e1

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