Skip to content
yararules.org
Menu

YARA · Signature Base (Florian Roth / Nextron)

SIGNATURE_BASE_WEBSHELL_ASPX_DLL_Moveit_Jun23_1

Detects compiled ASPX web shells found being used in MOVEit Transfer exploitation

WebshellSignature Base (Florian Roth / Nextron)Detection Rule License 1.1Compiles with YARA-X
Author
Florian Roth
Date
2023-06-01
Modified
2023-12-05
Score / Quality
85 / 85

What this rule detects

Detects compiled ASPX web shells found being used in MOVEit Transfer exploitation

Targets: Windows PE.

It defines 4 patterns (4 text, 0 hex, 0 regex).

Summary generated from the rule's metadata and condition.

Rule source

Download .yar
webshell-aspx-dll-moveit-jun23-1.yarDetection Rule License 1.1
rule SIGNATURE_BASE_WEBSHELL_ASPX_DLL_Moveit_Jun23_1 : FILE
{
	meta:
		description = "Detects compiled ASPX web shells found being used in MOVEit Transfer exploitation"
		author = "Florian Roth"
		id = "47db8602-9a9e-5efc-b8b9-fbc4f3c8d4e9"
		date = "2023-06-01"
		modified = "2023-12-05"
		reference = "https://www.trustedsec.com/blog/critical-vulnerability-in-progress-moveit-transfer-technical-analysis-and-recommendations/?utm_content=251159938&utm_medium=social&utm_source=twitter&hss_channel=tw-403811306"
		source_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/yara/vuln_moveit_0day_jun23.yar#L2-L22"
		license_url = "https://github.com/Neo23x0/signature-base/blob/94a1c48d7ab499879287ff611dfe7f9c56376030/LICENSE"
		hash = "6cbf38f5f27e6a3eaf32e2ac73ed02898cbb5961566bb445e3c511906e2da1fa"
		logic_hash = "47c2ec1e833852941434586b61d6f435b9acb32b2ff48e0a9e8006e0f9ff8056"
		score = 85
		quality = 85
		tags = "FILE"

	strings:
		$x1 = "human2_aspx" ascii fullword
		$x2 = "X-siLock-Comment" wide
		$x3 = "x-siLock-Step1" wide
		$a1 = "MOVEit.DMZ.Core.Data" ascii fullword

	condition:
		uint16( 0 ) == 0x5a4d and filesize < 40KB and ( 1 of ( $x* ) and $a1 ) or all of them
}

Strings (4 patterns)

IdentifierTypeValueModifiers
$x1text"human2_aspx"ascii fullword
$x2text"X-siLock-Comment"wide
$x3text"x-siLock-Step1"wide
$a1text"MOVEit.DMZ.Core.Data"ascii fullword

Condition

uint16( 0 ) == 0x5a4d and filesize < 40KB and ( 1 of ( $x* ) and $a1 ) or all of them

In plain words (Heuristic)

  • The file must start with “MZ” — a Windows executable (PE).
  • The file must be smaller than 40KB (a cheap guard that skips large files).
  • All patterns in the rule must match.
  • At least 1 patterns in ( $x* ) must match.
  • Pattern $a1 must be present.

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).

  • 6cbf38f5f27e6a3eaf32e2ac73ed02898cbb5961566bb445e3c511906e2da1fa

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: 47db8602-9a9e-5efc-b8b9-fbc4f3c8d4e9

Tags:FILE

Related rules