Check or Attack Name: ypmap

NIS (Network Information Service) contains data such as host files, password files, and e-mail aliases for entire networks. It allows a remote user to obtain copies of the NIS password map information. An attacker who possesses the NIS domain name (often set up as a derivative of the public domain name) can steal information helpful in guessing passwords and gaining unauthorized access.

Fortify the NIS domain name and use strong password techniques:

• The NIS domain name should be something hard to guess. If it can be guessed using brute force methods, then change the NIS domain name.
• In the event that an attacker successfully obtains the password file, the passwords should be hard to guess. The crack utility and password shadowing help correct this weakness, but NIS/YP (Yellow Pages) transfers include encrypted passwords even if they are shadowed and unreadable on the server. The attacker can decode them at leisure using brute force methods.