Skip to content

YARA · Google Cloud Threat Intelligence (GCTI)

GCTI_Cobaltstrike_Resources_Reverse_Bin_V2_5_Through_V4_X

Cobalt Strike's resources/reverse.bin signature for versions 2.5 to 4.x

Hack toolCobalt StrikeGoogle Cloud Threat Intelligence (GCTI)Apache License 2.0Compiles with YARA-X
Author
gssincla@google.com
Date
2022-11-18
Modified
2022-11-19
Score / Quality
75 / 85

What this rule detects

Cobalt Strike's resources/reverse.bin signature for versions 2.5 to 4.x

Associated malware family: Cobalt Strike.

It defines 3 patterns (0 text, 3 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

cobaltstrike-resources-reverse-bin-v2-5-through-v4-x.yarApache License 2.0
rule GCTI_Cobaltstrike_Resources_Reverse_Bin_V2_5_Through_V4_X
{
	meta:
		description = "Cobalt Strike's resources/reverse.bin signature for versions 2.5 to 4.x"
		author = "gssincla@google.com"
		id = "182dbcd0-1180-5516-abe3-cf2eebbd0e39"
		date = "2022-11-18"
		modified = "2022-11-19"
		reference = "https://cloud.google.com/blog/products/identity-security/making-cobalt-strike-harder-for-threat-actors-to-abuse"
		source_url = "https://github.com/chronicle/GCTI/blob/1c5fd42b1895098527fde00c2d9757edf6b303bb/YARA/CobaltStrike/CobaltStrike__Resources_Reverse_Bin_v2_5_through_v4_x.yara#L17-L104"
		license_url = "https://github.com/chronicle/GCTI/blob/1c5fd42b1895098527fde00c2d9757edf6b303bb/LICENSE"
		hash = "887f666d6473058e1641c3ce1dd96e47189a59c3b0b85c8b8fccdd41b84000c7"
		logic_hash = "c6c4fc477c7654ec07eb6ef4c6d53805a9b4881ba288754e1f50b3e4b134333c"
		score = 75
		quality = 85
		tags = ""

	strings:
		$apiLocator = {
			31 ?? 
			AC
			C1 ?? 0D 
			01 ?? 
			38 ?? 
			75 ?? 
			03 [2]
			3B [2]
			75 ?? 
			5? 
			8B ?? 24 
			01 ?? 
			66 8B [2]
			8B ?? 1C 
			01 ?? 
			8B ?? 8B 
			01 ?? 
			89 [3]
			5? 
			5? 
		}
		$ws2_32 = {
			5D
			68 33 32 00 00
			68 77 73 32 5F
		}
		$connect = {
			6A 10
			5? 
			5? 
			68 99 A5 74 61
		}

	condition:
		$apiLocator and $ws2_32 and $connect
}

Strings (3 patterns)

IdentifierTypeValueModifiers
$apiLocatorhex{ 31 ?? AC C1 ?? 0D 01 ?? 38 ?? 75 ?? 03 [2] 3B [2] 75 ?? 5? 8B ?? 24 01 ?? 66 8B [2] 8B ?? 1C 01 ?? …
$ws2_32hex{ 5D 68 33 32 00 00 68 77 73 32 5F }
$connecthex{ 6A 10 5? 5? 68 99 A5 74 61 }

Condition

$apiLocator and $ws2_32 and $connect

In plain words (Heuristic)

  • Pattern $apiLocator must be present.
  • Pattern $ws2_32 must be present.
  • Pattern $connect must be present.

Test this rule in your browser

Drop a file to scan it with this rule using YARA-X compiled to WebAssembly. Nothing is uploaded.

Drop a file here or click to chooseScanned locally with YARA-X. Files up to 200 MB.

Open in editor

References

Sample hashes

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

  • 887f666d6473058e1641c3ce1dd96e47189a59c3b0b85c8b8fccdd41b84000c7

Licence & attribution

Author: gssincla@google.com

Source repository: Google Cloud Threat Intelligence (GCTI) @ 1c5fd42b18

Licence: Apache License 2.0 (repository licence)

Original rule

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

Rule id: 182dbcd0-1180-5516-abe3-cf2eebbd0e39

More Cobalt Strike rules