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YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_EXPL_Cleo_Exploitation_JAVA_Payloads_Dec24_1_1

Detects characteristics of JAVA files used during Cleo software exploitation (as reported by Huntress in December 2024) - files Cli, ScSlot, Slot, SrvSlot

ExploitSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Florian Roth
Date
2024-12-10
Modified
2024-12-12
Score / Quality
75 / 85

What this rule detects

Detects characteristics of JAVA files used during Cleo software exploitation (as reported by Huntress in December 2024) - files Cli, ScSlot, Slot, SrvSlot

It defines 5 patterns (5 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

expl-cleo-exploitation-java-payloads-dec24-1-1.yarDetection Rule License 1.1
rule SIGNATURE_BASE_EXPL_Cleo_Exploitation_JAVA_Payloads_Dec24_1_1 : FILE
{
	meta:
		description = "Detects characteristics of JAVA files used during Cleo software exploitation (as reported by Huntress in December 2024) - files Cli, ScSlot, Slot, SrvSlot"
		author = "Florian Roth"
		id = "2940ddad-3dba-594a-9111-e4741d6ff39b"
		date = "2024-12-10"
		modified = "2024-12-12"
		reference = "https://www.huntress.com/blog/threat-advisory-oh-no-cleo-cleo-software-actively-being-exploited-in-the-wild"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/expl_cleo_dec24.yar#L224-L245"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "0c57b317b572d071afd8ccdb844dd6f117e20f818c6031d7ba8adcbd32be0617"
		logic_hash = "85600e9310e502b3b2135f2f3cf698ae54fe362047cdf9d378dcc107e0c2fa18"
		score = 75
		quality = 85
		tags = "FILE"

	strings:
		$a1 = "java/lang/StringBuffer"
		$x1 = "Start-Sleep 3;del " ascii
		$x2 = "sleep 3;rm -f '" ascii
		$x3 = "powershell -Noninteractive -EncodedCommand " ascii
		$x4 = "runDelFileCmd" ascii fullword

	condition:
		uint16( 0 ) == 0xfeca and filesize < 50KB and $a1 and 1 of ( $x* )
}

Strings (5 patterns)

IdentifierTypeValueModifiers
$a1text"java/lang/StringBuffer"
$x1text"Start-Sleep 3;del "ascii
$x2text"sleep 3;rm -f '"ascii
$x3text"powershell -Noninteractive -EncodedCommand "ascii
$x4text"runDelFileCmd"ascii fullword

Condition

uint16( 0 ) == 0xfeca and filesize < 50KB and $a1 and 1 of ( $x* )

In plain words (Heuristic)

  • The file must be smaller than 50KB (a cheap guard that skips large files).
  • At least 1 patterns in ( $x* ) must match.
  • Pattern $a1 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).

  • 0c57b317b572d071afd8ccdb844dd6f117e20f818c6031d7ba8adcbd32be0617

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: 2940ddad-3dba-594a-9111-e4741d6ff39b

Tags:FILE