Cybercriminals can weaponize Windows LNK (shortcut) files to execute malicious code without user interaction, even bypassing the need for a click. When a victim right-clicks or hovers over a malicious LNK file, their system may automatically send their NTLM hash to an attacker-controlled server, enabling credential theft and lateral movement.
Source: LNK Exploit Details
You Should Know:
1. How the Attack Works
- Attackers craft malicious LNK files with embedded scripts or UNC paths.
- When a user interacts with the file (right-click, hover, or preview), Windows initiates an SMB/NTLM authentication request.
- The attacker captures the NTLM hash and can relay it or crack it offline.
2. Detection & Prevention
Commands to Check Suspicious LNK Files
Analyze LNK file properties Get-ChildItem -Path "C:\Users\Public" -Filter .lnk -Recurse | Select-Object Name, TargetPath Disable WebClient service (prevents some UNC-based attacks) Stop-Service WebClient -Force Set-Service WebClient -StartupType Disabled
Group Policy Adjustments
Disable NTLM authentication (where possible) gpedit.msc → Computer Config → Windows Settings → Security Settings → Local Policies → Security Options → "Network security: Restrict NTLM: Outgoing NTLM traffic" → Deny All
3. Mitigation Steps
- Block Outbound SMB (TCP 445) at the firewall.
- Enable SMB Signing to prevent relay attacks:
Set-SmbClientConfiguration -RequireSecuritySignature $true
- Use LNK File Analyzers like LNK Parser.
4. Zero-Click Exploit Countermeasures
- Disable file previews in Windows Explorer:
reg add "HKCU\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer" /v "NoRecentDocsHistory" /t REG_DWORD /d 1 /f
- Apply Microsoft’s CVE-2023-32049 patch (if applicable).
What Undercode Say
LNK-based attacks remain a stealthy threat, especially in phishing campaigns. Defenders must:
– Monitor SMB outbound connections (e.g., via Wireshark or Zeek).
– Enforce NTLMv2 and disable legacy protocols.
– Train users to avoid downloading LNK files from untrusted sources.
For advanced hunters:
Hunt for suspicious LNK files in logs (Linux/WSL) grep -r ".lnk" /var/log/
Windows defenders should log LNK file executions via Sysmon (Event ID 1 with `.lnk` in CommandLine).
Prediction
As Microsoft hardens Office macros, attackers will increasingly abuse LNK files, ISO images, and other “trusted” Windows features for initial access. Expect more zero-click LNK exploits in 2024-2025.
Expected Output:
- Malicious LNK file analysis
- NTLM hash theft prevention
- Zero-click mitigation steps
References:
Reported By: Mamun Infosec – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅
