Pass the hash

In computer security, pass the hash is a hacking technique that allows an attacker to authenticate to a remote server or service by using the underlying NTLM or LanMan hash of a user's password, instead of requiring the associated plaintext password as is normally the case. It replaces the need for stealing the plaintext password to gain access with stealing the hash.

The attack exploits an implementation weakness in the authentication protocol, where password hashes remain static from session to session until the password is next changed.

This technique can be performed against any server or service accepting LM or NTLM authentication, whether it runs on a machine with Windows, Unix, or any other operating system.