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👉 What is Link-Local Multicast Name Resolution (LLMNR)?
LLMNR is a protocol based on the DNS packet format that allows IPv4 and IPv6 hosts to resolve hostnames on the same local network without relying on a DNS server. It is commonly used when DNS resolution fails, enabling devices to communicate directly within the local network.
👉 How does LLMNR work?
When a device needs to resolve a hostname, it sends an LLMNR query to a multicast group address. All devices on the network receive this query, and if a device recognizes the hostname, it responds with the corresponding IP address. However, LLMNR transmits data in plaintext, making it vulnerable to attacks like LLMNR poisoning.
👉 LLMNR Poisoning with Responder
Responder is a powerful tool used to exploit LLMNR vulnerabilities. It listens for LLMNR, NBT-NS (NetBIOS Name Service), and MDNS (Multicast DNS) traffic, intercepting authentication attempts and capturing usernames and password hashes. These hashes can later be cracked using tools like Hashcat.
Practice-Verified Commands and Codes:
1. Install Responder:
git clone https://github.com/lgandx/Responder.git cd Responder sudo python3 Responder.py -I eth0
2. Capture LLMNR Traffic:
Run Responder on your network interface to capture LLMNR requests:
sudo python3 Responder.py -I eth0 -wrf
3. Crack Hashes with Hashcat:
Once you capture an NTLMv2 hash, use Hashcat to crack it:
hashcat -m 5600 captured_hash.txt /path/to/wordlist.txt
4. Disable LLMNR on Windows:
To prevent LLMNR poisoning, disable LLMNR on Windows systems:
Set-ItemProperty -Path "HKLM:\Software\Policies\Microsoft\Windows NT\DNSClient" -Name "EnableMulticast" -Value 0
5. Disable LLMNR on Linux:
On Linux, you can disable LLMNR by editing the `/etc/nsswitch.conf` file:
sudo nano /etc/nsswitch.conf
Change the `hosts` line to:
hosts: files dns
What Undercode Say:
LLMNR poisoning is a critical vulnerability that exploits the lack of encryption in the LLMNR protocol. By using tools like Responder, attackers can intercept sensitive information, such as usernames and password hashes, which can later be cracked using tools like Hashcat. To mitigate this risk, it is essential to disable LLMNR on all systems within your network. On Windows, this can be done via the registry, while on Linux, modifying the `/etc/nsswitch.conf` file is effective. Additionally, network administrators should enforce the use of secure protocols like DNS over HTTPS (DoH) or DNS over TLS (DoT) to ensure encrypted name resolution. Regularly monitoring network traffic for unusual LLMNR or NBT-NS activity can also help detect potential attacks. For further reading on securing your network, refer to OWASP’s Guide to LLMNR/NBT-NS Exploitation. Always stay vigilant and keep your systems updated to protect against evolving cyber threats.
References:
Hackers Feeds, Undercode AI
