YARA · ESET malware-ioc

ESET_Apt_Windows_Invisimole_Wrapper_DLL

Detects InvisiMole wrapper DLL with embedded RC2CL and RC2FM backdoors, by export and resource names

APT / threat actorInvisimoleESET malware-iocBSD 2-Clause LicenseCompiles with YARA-X (with warnings)

Author: ESET Research
Date: 2021-05-17
Score / Quality: 75 / 80

What this rule detects

Detects InvisiMole wrapper DLL with embedded RC2CL and RC2FM backdoors, by export and resource names

Associated malware family: Invisimole.

Targets: Windows PE.

It has no patterns: the condition alone decides (modules, file properties or other rules). YARA modules used: pe.

YARA-X says: warning[deprecated_field]: field `number_of_resources` is deprecated

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

Includes the imports needed to compile it on its own.

apt-windows-invisimole-wrapper-dll.yarBSD 2-Clause License

import "pe"

rule ESET_Apt_Windows_Invisimole_Wrapper_DLL
{
	meta:
		description = "Detects InvisiMole wrapper DLL with embedded RC2CL and RC2FM backdoors, by export and resource names"
		author = "ESET Research"
		id = "b9609b09-3ef5-5793-a3aa-4692cec367d9"
		date = "2021-05-17"
		modified = "2021-05-17"
		reference = "https://github.com/eset/malware-ioc/"
		source_url = "https://github.com/eset/malware-ioc/blob/17baf44964a77368e9149f4f593eb098beddf1c5/invisimole/invisimole.yar#L120-L138"
		license_url = "https://github.com/eset/malware-ioc/blob/17baf44964a77368e9149f4f593eb098beddf1c5/LICENSE"
		logic_hash = "156bc5bc7b0ed5c77a5a15e7799a3077d40150896476a60935cf21a9afe36856"
		score = 75
		quality = 80
		tags = ""
		license = "BSD 2-Clause"
		version = "1"

	condition:
		pe.exports( "GetDataLength" ) and for any y in ( 0 .. pe.number_of_resources - 1 ) : ( pe.resources [ y ] . type == pe.RESOURCE_TYPE_RCDATA and pe.resources [ y ] . name_string == "R\x00C\x002\x00C\x00L\x00" ) and for any y in ( 0 .. pe.number_of_resources - 1 ) : ( pe.resources [ y ] . type == pe.RESOURCE_TYPE_RCDATA and pe.resources [ y ] . name_string == "R\x00C\x002\x00F\x00M\x00" )
}

Condition

pe.exports( "GetDataLength" ) and for any y in ( 0 .. pe.number_of_resources - 1 ) : ( pe.resources [ y ] . type == pe.RESOURCE_TYPE_RCDATA and pe.resources [ y ] . name_string == "R\x00C\x002\x00C\x00L\x00" ) and for any y in ( 0 .. pe.number_of_resources - 1 ) : ( pe.resources [ y ] . type == pe.RESOURCE_TYPE_RCDATA and pe.resources [ y ] . name_string == "R\x00C\x002\x00F\x00M\x00" )

In plain words (Heuristic)

A for-loop checks a property over several matches or items.
Uses the pe module.
Checks exported functions or the DLL name.

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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: b9609b09-3ef5-5793-a3aa-4692cec367d9

Metadata

version	1

ESET_Apt_Windows_Invisimole
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