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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_MAL_MSI_Mpyutils_Feb24_1

Detects malicious MSI package 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
70 / 85

What this rule detects

Detects malicious MSI package mentioned in a HuntressLabs report on the exploitation of ScreenConnect vulnerability CVE-2024-1708 and CVE-2024-1709

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

Summary generated from the rule's metadata and condition.

Rule source

mal-msi-mpyutils-feb24-1.yarDetection Rule License 1.1
rule SIGNATURE_BASE_MAL_MSI_Mpyutils_Feb24_1 : CVE_2024_1708 CVE_2024_1709 FILE
{
	meta:
		description = "Detects malicious MSI package mentioned in a HuntressLabs report on the exploitation of ScreenConnect vulnerability CVE-2024-1708 and CVE-2024-1709"
		author = "Florian Roth"
		id = "e7794336-a325-5b92-8c25-81ed9cb28044"
		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#L230-L247"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "8e51de4774d27ad31a83d5df060ba008148665ab9caf6bc889a5e3fba4d7e600"
		logic_hash = "ba20db486e5d3c29c9702e10628fb3c0e55e52bbec74e3a86ed6511a6475b82f"
		score = 70
		quality = 85
		tags = "CVE-2024-1708, CVE-2024-1709, FILE"

	strings:
		$s1 = "crypt64ult.exe" ascii fullword
		$s2 = "EXPAND.EXE" wide fullword
		$s6 = "ICACLS.EXE" wide fullword

	condition:
		uint16( 0 ) == 0xcfd0 and filesize < 20000KB and all of them
}

Strings (3 patterns)

IdentifierTypeValueModifiers
$s1text"crypt64ult.exe"ascii fullword
$s2text"EXPAND.EXE"wide fullword
$s6text"ICACLS.EXE"wide fullword

Condition

uint16( 0 ) == 0xcfd0 and filesize < 20000KB and all of them

In plain words (Heuristic)

  • The file must be smaller than 20000KB (a cheap guard that skips large files).
  • All patterns in the rule must match.

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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).

  • 8e51de4774d27ad31a83d5df060ba008148665ab9caf6bc889a5e3fba4d7e600

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: e7794336-a325-5b92-8c25-81ed9cb28044

Tags:CVE_2024_1708CVE_2024_1709FILE