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GCTI_Cobaltstrike_Resources_Smbstager_Bin_V2_5_Through_V4_X

Cobalt Strike's resources/smbstager.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/smbstager.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-smbstager-bin-v2-5-through-v4-x.yarApache License 2.0
rule GCTI_Cobaltstrike_Resources_Smbstager_Bin_V2_5_Through_V4_X
{
	meta:
		description = "Cobalt Strike's resources/smbstager.bin signature for versions 2.5 to 4.x"
		author = "gssincla@google.com"
		id = "074b7d83-e3d8-541c-804b-2417c21f54d5"
		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_Smbstager_Bin_v2_5_through_v4_x.yara#L17-L95"
		license_url = "https://github.com/chronicle/GCTI/blob/1c5fd42b1895098527fde00c2d9757edf6b303bb/LICENSE"
		hash = "946af5a23e5403ea1caccb2e0988ec1526b375a3e919189f16491eeabc3e7d8c"
		logic_hash = "b0f6535069df16a64de44ca0638ec060c1ff264a7820c94710d61ca7e8474450"
		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? 
		}
		$smb = { 68 C6 96 87 52 }
		$smbstart = {
			6A 40
			68 00 10 00 00
			68 FF FF 07 00
			6A 00
			68 58 A4 53 E5
		}

	condition:
		$apiLocator and $smb and $smbstart
}

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 ?? …
$smbhex{ 68 C6 96 87 52 }
$smbstarthex{ 6A 40 68 00 10 00 00 68 FF FF 07 00 6A 00 68 58 A4 53 E5 }

Condition

$apiLocator and $smb and $smbstart

In plain words (Heuristic)

  • Pattern $apiLocator must be present.
  • Pattern $smb must be present.
  • Pattern $smbstart must be present.

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References

Sample hashes

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

  • 946af5a23e5403ea1caccb2e0988ec1526b375a3e919189f16491eeabc3e7d8c

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: 074b7d83-e3d8-541c-804b-2417c21f54d5

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