YARA · WithSecure Labs IOCs

WITHSECURELABS_SILKLOADER

Detects SILKLOADER samples

GenericWithSecure Labs IOCsBSD 2-Clause LicenseCompiles with YARA-X (with warnings)

Author: WithSecure
Date: 2023-03-15
Score / Quality: 75 / 75

What this rule detects

Detects SILKLOADER samples

Targets: Windows PE.

It defines 2 patterns (0 text, 2 hex, 0 regex). YARA modules used: pe.

YARA-X says: warning[non_bool_expr]: non-boolean expression used as boolean

Summary generated from the rule's metadata and condition.

Rule source

Download .yar

Includes the imports needed to compile it on its own.

silkloader.yarBSD 2-Clause License

import "pe"

rule WITHSECURELABS_SILKLOADER
{
	meta:
		description = "Detects SILKLOADER samples"
		author = "WithSecure"
		id = "bb8a543e-fdbf-5be1-901e-3e2a9965fd62"
		date = "2023-03-15"
		modified = "2023-03-15"
		reference = "https://labs.withsecure.com/publications/silkloader"
		source_url = "https://github.com/WithSecureLabs/iocs/blob/1a8384468dd292c6d2c5114c32e42dc0da1f5ae1/SILKLOADER/silkloader.yar#L2-L20"
		license_url = "https://github.com/WithSecureLabs/iocs/blob/1a8384468dd292c6d2c5114c32e42dc0da1f5ae1/LICENSE"
		hash = "c83ac6dc96febd49c7c558e8cf85dd8bcb3a84fdc78b3ba72ebf681566dc1865"
		hash = "e4dadabd1cee7215ff6e31e01f6b0dd820851685836592a14f982f2c7972fc25"
		hash = "d77a59e6ba3a8f3c000a8a8955af77d2898f220f7bf3c0968bf0d7c8ac25a5ad"
		logic_hash = "48aa249ea78e5a3bfe9934fd0dfa26b79f9e6cbe1e5b1426b84f8d8a3d77d742"
		score = 75
		quality = 75
		tags = ""
		version = "1.0"

	strings:
		$str1 = {5400520041004e005300460045005200}
		$str2 = {760062006300630073006200}

	condition:
		pe.is_pe and pe.characteristics & pe.DLL and all of them
}

Strings (2 patterns)

Identifier	Type	Value	Modifiers
$str1	hex	{5400520041004e005300460045005200}
$str2	hex	{760062006300630073006200}

Condition

pe.is_pe and pe.characteristics & pe.DLL 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.
Uses the pe module.
Requires a DLL.

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References

https://labs.withsecure.com/publications/silkloader

Sample hashes

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

c83ac6dc96febd49c7c558e8cf85dd8bcb3a84fdc78b3ba72ebf681566dc1865
e4dadabd1cee7215ff6e31e01f6b0dd820851685836592a14f982f2c7972fc25
d77a59e6ba3a8f3c000a8a8955af77d2898f220f7bf3c0968bf0d7c8ac25a5ad

Licence & attribution

Author: WithSecure

Source repository: WithSecure Labs IOCs @ 1a8384468d

Licence: BSD 2-Clause License (repository licence)

Original rule

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

Rule id: bb8a543e-fdbf-5be1-901e-3e2a9965fd62

Metadata

version	1.0

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