When you click the Password Restrictions button on the Registered Users tab in the Security dialog box, the Password Restrictions dialog box appears. There are three options that may increase the security of the passwords used by your Registered Users.
Passwords Can't Match the Three Previous Passwords prevents the Registered User from reusing recently-used passwords.
Minimum Number of Characters in Passwords requires Registered Users to choose passwords of a minimum length, which may make them more difficult to guess.
Number of Days Until Password Expires requires Registered Users to create new passwords on a regular basis.