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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_MAL_CS_Loader_Feb24_1

Detects Cobalt Strike malware samples mentioned in a HuntressLabs report on the exploitation of ScreenConnect vulnerability CVE-2024-1708 and CVE-2024-1709

MalwareSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Florian Roth
Date
2024-02-23
Modified
2024-04-24
Score / Quality
75 / 85

What this rule detects

Detects Cobalt Strike malware samples mentioned in a HuntressLabs report on the exploitation of ScreenConnect vulnerability CVE-2024-1708 and CVE-2024-1709

Targets: Windows PE.

It defines 1 patterns (1 text, 0 hex, 0 regex). YARA modules used: pe.

Summary generated from the rule's metadata and condition.

Rule source

Includes the imports needed to compile it on its own.

mal-cs-loader-feb24-1.yarDetection Rule License 1.1
import "pe"

rule SIGNATURE_BASE_MAL_CS_Loader_Feb24_1 : CVE_2024_1708 CVE_2024_1709 FILE
{
	meta:
		description = "Detects Cobalt Strike malware samples mentioned in a HuntressLabs report on the exploitation of ScreenConnect vulnerability CVE-2024-1708 and CVE-2024-1709"
		author = "Florian Roth"
		id = "6c9914a4-b079-5a39-9d3b-7b9a2b54dc2b"
		date = "2024-02-23"
		modified = "2024-04-24"
		reference = "https://www.huntress.com/blog/slashandgrab-screen-connect-post-exploitation-in-the-wild-cve-2024-1709-cve-2024-1708"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/expl_connectwise_screenconnect_vuln_feb24.yar#L186-L206"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "0a492d89ea2c05b1724a58dd05b7c4751e1ffdd2eab3a2f6a7ebe65bf3fdd6fe"
		logic_hash = "ae0e25c2dda1b727978977c674e834cd659661c597d88395a6f46ad5a179e9f0"
		score = 75
		quality = 85
		tags = "CVE-2024-1708, CVE-2024-1709, FILE"

	strings:
		$s1 = "Dll_x86.dll" ascii fullword

	condition:
		uint16( 0 ) == 0x5a4d and filesize < 1000KB and ( pe.exports ( "UpdateSystem" ) and ( pe.imphash ( ) == "0dc05c4c21a86d29f1c3bf9cc5b712e0" or $s1 ) )
}

Strings (1 patterns)

IdentifierTypeValueModifiers
$s1text"Dll_x86.dll"ascii fullword

Condition

uint16( 0 ) == 0x5a4d and filesize < 1000KB and ( pe.exports ( "UpdateSystem" ) and ( pe.imphash ( ) == "0dc05c4c21a86d29f1c3bf9cc5b712e0" or $s1 ) )

In plain words (Heuristic)

  • The file must start with “MZ” — a Windows executable (PE).
  • The file must be smaller than 1000KB (a cheap guard that skips large files).
  • Uses the pe module.
  • Pattern $s1 must be present.
  • Checks the PE import hash (imphash).
  • Checks exported functions or the DLL name.

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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).

  • 0a492d89ea2c05b1724a58dd05b7c4751e1ffdd2eab3a2f6a7ebe65bf3fdd6fe

Licence & attribution

Author: Florian Roth

Source repository: Signature Base (Florian Roth / Nextron) @ 94a1c48d7a

Licence: Detection Rule License 1.1 (repository licence)

Original rule

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

Rule id: 6c9914a4-b079-5a39-9d3b-7b9a2b54dc2b

Tags:CVE_2024_1708CVE_2024_1709FILE