Responder - Ultimate Guide
Responder - Info
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Responder an LLMNR, NBT-NS and MDNS poisoner. It will answer to specific NBT-NS (NetBIOS Name Service) queries based on their name suffix (see: By default, the tool will only answer to File Server Service request, which is for SMB.

The concept behind this is to target our answers, and be stealthier on the network. This also helps to ensure that we don’t break legitimate NBT-NS behavior. You can set the -r option via command line if you want to answer to the Workstation Service request name suffix.


Built-in SMB Auth server.

Supports NTLMv1, NTLMv2 hashes with Extended Security NTLMSSP by default. Successfully tested from Windows 95 to Server 2012 RC, Samba and Mac OSX Lion. Clear text password is supported for NT4, and LM hashing downgrade when the –lm option is set. This functionality is enabled by default when the tool is launched.

Built-in MSSQL Auth server.

In order to redirect SQL Authentication to this tool, you will need to set the option -r (NBT-NS queries for SQL Server lookup are using the Workstation Service name suffix) for systems older than windows Vista (LLMNR will be used for Vista and higher). This server supports NTLMv1, LMv2 hashes. This functionality was successfully tested on Windows SQL Server 2005 & 2008.

Built-in HTTP Auth server.

In order to redirect HTTP Authentication to this tool, you will need to set the option -r for Windows version older than Vista (NBT-NS queries for HTTP server lookup are sent using the Workstation Service name suffix). For Vista and higher, LLMNR will be used. This server supports NTLMv1, NTLMv2 hashes and Basic Authentication. This server was successfully tested on IE 6 to IE 10, Firefox, Chrome, Safari.

Note: This module also works for WebDav NTLM authentication issued from Windows WebDav clients (WebClient). You can now send your custom files to a victim.

Built-in HTTPS Auth server.

Same as above. The folder certs/ contains 2 default keys, including a dummy private key. This is intentional, the purpose is to have Responder working out of the box. A script was added in case you need to generate your own self signed key pair.

Built-in LDAP Auth server.

In order to redirect LDAP Authentication to this tool, you will need to set the option -r for Windows version older than Vista (NBT-NS queries for HTTP server lookup are sent using the Workstation Service name suffix). For Vista and higher, LLMNR will be used. This server supports NTLMSSP hashes and Simple Authentication (clear text authentication). This server was successfully tested on Windows Support tool “ldp” and LdapAdmin.

Built-in FTP, POP3, IMAP, SMTP Auth servers.

This modules will collect clear text credentials.

Built-in DNS server.

This server will answer type A queries. This is really handy when it’s combined with ARP spoofing.

Built-in WPAD Proxy Server.

This module will capture all HTTP requests from anyone launching Internet Explorer on the network if they have “Auto-detect settings” enabled. This module is highly effective. You can configure your custom PAC script in Responder.conf and inject HTML into the server’s responses. See Responder.conf.

Browser Listener

This module allows to find the PDC in stealth mode.


When the option -f is used, Responder will fingerprint every host who issued an LLMNR/NBT-NS query. All capture modules still work while in fingerprint mode.

Icmp Redirect

 python tools/

For MITM on Windows XP/2003 and earlier Domain members. This attack combined with the DNS module is pretty effective.

Rogue DHCP

 python tools/

DHCP Inform Spoofing. Allows you to let the real DHCP Server issue IP addresses, and then send a DHCP Inform answer to set your IP address as a primary DNS server, and your own WPAD URL.

Analyze mode.

This module allows you to see NBT-NS, BROWSER, LLMNR, DNS requests on the network without poisoning any responses. Also, you can map domains, MSSQL servers, workstations passively, see if ICMP Redirects attacks are plausible on your subnet.


All hashes are printed to stdout and dumped in an unique file John Jumbo compliant, using this format:


Log files are located in the “logs/” folder. Hashes will be logged and printed only once per user per hash type, unless you are using the Verbose mode (-v).

Responder will logs all its activity to Responder-Session.log
Analyze mode will be logged to Analyze-Session.log
Poisoning will be logged to Poisoners-Session.log

Additionally, all captured hashed are logged into an SQLite database which you can configure in Responder.conf


First of all, please take a look at Responder.conf and tweak it for your needs.

Running the tool:

./ [options]

Typical Usage Example:

./ -I eth0 -wrf


  --version             show program's version number and exit
  -h, --help            show this help message and exit
  -A, --analyze         Analyze mode. This option allows you to see NBT-NS,
                        BROWSER, LLMNR requests without responding.
  -I eth0, --interface=eth0
                        Network interface to use
  -b, --basic           Return a Basic HTTP authentication. Default: NTLM
  -r, --wredir          Enable answers for netbios wredir suffix queries.
                        Answering to wredir will likely break stuff on the
                        network. Default: False
  -d, --NBTNSdomain     Enable answers for netbios domain suffix queries.
                        Answering to domain suffixes will likely break stuff
                        on the network. Default: False
  -f, --fingerprint     This option allows you to fingerprint a host that
                        issued an NBT-NS or LLMNR query.
  -w, --wpad            Start the WPAD rogue proxy server. Default value is
  -u UPSTREAM_PROXY, --upstream-proxy=UPSTREAM_PROXY
                        Upstream HTTP proxy used by the rogue WPAD Proxy for
                        outgoing requests (format: host:port)
  -F, --ForceWpadAuth   Force NTLM/Basic authentication on wpad.dat file
                        retrieval. This may cause a login prompt. Default:
  --lm                  Force LM hashing downgrade for Windows XP/2003 and
                        earlier. Default: False
  -v, --verbose         Increase verbosity.


•This tool listens on several ports: UDP 137, UDP 138, UDP 53, UDP/TCP 389,TCP 1433, TCP 80, TCP 139, TCP 445, TCP 21, TCP 3141,TCP 25, TCP 110, TCP 587 and Multicast UDP 5553.

•If you run Samba on your system, stop smbd and nmbd and all other services listening on these ports.

•For Ubuntu users:

     Edit this file /etc/NetworkManager/NetworkManager.conf and comment the line: dns=dnsmasq. Then kill dnsmasq with this command (as root): killall dnsmasq -9 

•Any rogue server can be turned off in Responder.conf.

•This tool is not meant to work on Windows.

•For OSX, please note: Responder must be launched with an IP address for the -i flag (e.g. -i YOUR_IP_ADDR). There is no native support in OSX for custom interface binding. Using -i en1 will not work. Also to run Responder with the best experience, run the following as root:

    launchcl unload /System/Library/LaunchDaemons/

    launchctl unload /System/Library/LaunchDaemons/

    launchctl unload /System/Library/LaunchDaemons/

    launchctl unload /System/Library/LaunchDaemons/

Whats is a LLMNR & NBT-NS Spoofing Attack?

A LLMNR & NBT-NS Spoofing Attack is a classic internal network attack that still works today, due to low awareness and the fact it’s enabled by default in Windows. This document explains what a LLMNR & NBT-NS attack is, how to use the attack on a penetration test and finally, how to secure networks against the vulnerability.

What is LLMNR & NetBIOS Name Server Broadcast?

When a DNS name server request fails Microsoft windows systems use Link-Local Multicast Name Resolution (LLMNR for short) and the Net-BIOS Name Service (NBT-NS) for fallback name resolution.

What’s the issue with LLMNR & Netbios NS Broadcasting?

If the DNS name does not resolve, the client performs a unauthenticated UDP broadcast to the network asking if any other system has the name it’s looking for. The fact this process is unauthenticated and broadcasted to the whole network allows any machine on the network to respond and claim to be the target machine.

What is a LLMNR / NBT-NS Poisoning Attack?

By listening for LLMNR & NetBIOS broadcasts it’s possible to masquerade as the machine (spoof) the client is erroneously trying to authenticate with. After accepting the connection it’s possible to use a tool like or Metasploit to forward on requests to a rogue service (like SMB TCP: 137) that performs the authentication process. During the authentication process the client will send the rogue server a NTLMv2 hash for the user that’s trying to authenticate, this hash is captured to disk and can be cracked offline with a tool like Hashcat or John the Ripper (TJR) or used in a pass-the-hash attack.LLMNR and NBT-NS are enabled by default in Windows and with awareness of this attack being fairly low you stand a good chance of being able to gather credentials on an internal penetration test. Leave running during an engagement while you’re working other attack vectors.

What about Linux & Apple clients, are they Vulnerable?

Yes, Linux and Apple clients use a similar protocol called multicast DNS or mDNS for short which listens on TCP: 5353. For more information on mDSN see the mDNS wikipedia page Typical LLMNR / NetBIOS Name Server Attack

The diagram below shows the typical scenario for this type of attack where a user mistypes a server name.

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