Detect Windows NTLM Credential Leak via File Download Interaction in Google Chronicle
CVE-2025-24054 is a Windows NTLM hash disclosure vulnerability triggered when a user interacts with a specially crafted file (e.g., .library-ms, .url, .lnk) that forces an outbound NTLM authentication attempt to an attacker-controlled server. Exploitation requires minimal user interaction — simply downloading or viewing a malicious file in Explorer can suffice. The leaked Net-NTLMv2 hash can be cracked offline or relayed for lateral movement. This vulnerability is actively exploited in the wild and listed in CISA's KEV catalog.
MITRE ATT&CK
YARA-L Detection Query
rule cve_2025_24054_ntlm_credential_leak {
meta:
author = "df00tech Detection Engineering"
description = "Detects CVE-2025-24054 NTLM credential leakage via crafted file interaction triggering outbound SMB authentication"
severity = "HIGH"
priority = "HIGH"
reference = "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2025-24054"
cve = "CVE-2025-24054"
events:
$file_event.metadata.event_type = "FILE_CREATION"
$file_event.target.file.full_path = /(?i)\.(library-ms|url|lnk|scf)$/
$file_event.principal.hostname = $hostname
$file_event.principal.process.file.full_path = /(?i)(explorer|svchost|chrome|msedge|firefox)\.exe$/
$network_event.metadata.event_type = "NETWORK_CONNECTION"
$network_event.target.port = 445
$network_event.principal.hostname = $hostname
$network_event.target.ip != "10.0.0.0/8"
$network_event.target.ip != "172.16.0.0/12"
$network_event.target.ip != "192.168.0.0/16"
match:
$hostname over 30s
condition:
$file_event and $network_event
}Chronicle YARA-L rule that correlates file creation events for NTLM-triggering file types with outbound SMB port 445 connections to non-private IPs within 30 seconds on the same host, detecting CVE-2025-24054 exploitation attempts.
Data Sources
Required Tables
False Positives & Tuning
- Legitimate .lnk files on user desktops pointing to mapped SMB drives used daily
- Enterprise software deployment tools distributing .url shortcuts to internal resources
- Network attached storage accessed via Windows Explorer with library files
- IT helpdesk creating .library-ms files during system configuration
Other platforms for CVE-2025-24054
Testing Methodology
Validate this detection against 4 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1NTLM Credential Leak via Malicious .library-ms File
Expected signal: Sysmon Event ID 11 (FileCreate) for TestLib.library-ms; Sysmon Event ID 3 (NetworkConnect) from explorer.exe to ATTACKER_IP:445; Windows Security Event ID 4648 showing NTLM authentication attempt to ATTACKER_IP
- Test 2NTLM Credential Leak via Crafted .url Shortcut File
Expected signal: Sysmon Event ID 11 (FileCreate) for Important-Document.url on Desktop; Sysmon Event ID 3 (NetworkConnect) from explorer.exe to ATTACKER_IP:445; Windows Security Event ID 4625 if auth fails (Responder returns failure after capture)
- Test 3Net-NTLMv2 Hash Offline Cracking Simulation Post-Capture
Expected signal: On Windows DC (if auth attempted with cracked hash): Windows Security Event ID 4624 (successful logon) or 4625 (failed logon) with NTLM authentication from unexpected source IP; Kerberos fallback to NTLM is itself anomalous for modern AD environments
- Test 4NTLM Credential Leak via Crafted .scf File in Shared Folder
Expected signal: Sysmon Event ID 11 (FileCreate) for @trigger.scf; Sysmon Event ID 3 (NetworkConnect) from explorer.exe to ATTACKER_IP:445 triggered by shell icon resolution; Windows Security audit log showing NTLM authentication to external host
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