Accounts with known default passwords Intruders often exploit system default passwords that have not been changed since installation. Make sure to change all default passwords when the software is installed. Be aware that product upgrades can quietly change account passwords to a new default. It is best to change the passwords of default accounts after updates are applied. Accounts no longer in use should be removed from the authorization file and rights database.
Intruders also try guessing simple user passwords.
See the discussion on weak passwords in Section A for suggestions on choosing good passwords. If an intruder gets into a system, the programs patch.exe, loginout.exe, and show.exe are often modified. Compare these programs with those found in your distribution media. If your UNIX system has a shadow password capability, you should consider using it. Instead the encrypted passwords are held in a shadow file that is not world readable.