Skip to content

YARA · Google Cloud Threat Intelligence (GCTI)

GCTI_Cobaltstrike_Sleeve_Beaconloader_VA_X64_O_V4_3_V4_4_V4_5_And_V4_6

Cobalt Strike's sleeve/BeaconLoader.VA.x64.o (VirtualAlloc) Versions 4.3 through at least 4.6

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 sleeve/BeaconLoader.VA.x64.o (VirtualAlloc) Versions 4.3 through at least 4.6

Associated malware family: Cobalt Strike.

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

Summary generated from the rule's metadata and condition.

Rule source

cobaltstrike-sleeve-beaconloader-va-x64-o-v4-3-v4-4-v4-5-and-v4-6.yarApache License 2.0
rule GCTI_Cobaltstrike_Sleeve_Beaconloader_VA_X64_O_V4_3_V4_4_V4_5_And_V4_6
{
	meta:
		description = "Cobalt Strike's sleeve/BeaconLoader.VA.x64.o (VirtualAlloc) Versions 4.3 through at least 4.6"
		author = "gssincla@google.com"
		id = "8ca04f82-a8a8-5162-8b0c-8a7bce678a85"
		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__Sleeve_BeaconLoader_all.yara#L376-L456"
		license_url = "https://github.com/chronicle/GCTI/blob/1c5fd42b1895098527fde00c2d9757edf6b303bb/LICENSE"
		hash = "ac090a0707aa5ccd2c645b523bd23a25999990cf6895fce3bfa3b025e3e8a1c9"
		logic_hash = "17402e952d71d02274a9b2814512b28a402e8d11a6c2a2375844fe24719f87a6"
		score = 75
		quality = 85
		tags = ""

	strings:
		$core_sig = {
      C6 44 24 48 56
      C6 44 24 49 69
      C6 44 24 4A 72
      C6 44 24 4B 74
      C6 44 24 4C 75
      C6 44 24 4D 61
      C6 44 24 4E 6C
      C6 44 24 4F 41
      C6 44 24 50 6C
      C6 44 24 51 6C
      C6 44 24 52 6F
      C6 44 24 53 63
      C6 44 24 54 00
    }
		$deobfuscator = {
      8B 04 24
      FF C0
      89 04 24
      8B 44 24 28
      39 04 24
      73 20
      8B 04 24
      0F B6 4C 24 30
      48 8B 54 24 20
      0F BE 04 02
      33 C1
      8B 0C 24
      48 8B 54 24 20
      88 04 0A
    }

	condition:
		all of them
}

Strings (2 patterns)

IdentifierTypeValueModifiers
$core_sighex{ C6 44 24 48 56 C6 44 24 49 69 C6 44 24 4A 72 C6 44 24 4B 74 C6 44 24 4C 75 C6 44 24 4D 61 C6 44 24 4E 6C C6 44 …
$deobfuscatorhex{ 8B 04 24 FF C0 89 04 24 8B 44 24 28 39 04 24 73 20 8B 04 24 0F B6 4C 24 30 48 8B 54 24 20 0F BE 04 …

Condition

all of them

In plain words (Heuristic)

  • All patterns in the rule must match.

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).

  • ac090a0707aa5ccd2c645b523bd23a25999990cf6895fce3bfa3b025e3e8a1c9

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: 8ca04f82-a8a8-5162-8b0c-8a7bce678a85

More Cobalt Strike rules