Reusable Passwords. The most common method of password to the system once and then reuses it to gain future access. The quality of the security that a reusable password provides depends on the quality of the password itself. If the password itself. If the password pertains to something personal about the user, such as a child’s name, pet’s name, birth date, or hair color, a computer criminal can often deduce it. Even if the password is derived from nonpersonal data, it may be weak. For example, a string of keystrokes (such as A-S-D-F) or the same letter used multiple times can easily be cracked. Passwords that contain random letters and digits are more difficult to crack, but are also more difficult for the user to remember.
To improve access control, management should require that passwords be changed regularly and disallow weak passwords. Software is available that automatically scans password files and notifies users that their passwords have expired and need to be changed. These systems also use extensive databases of know weak passwords to validate the new password and disallow weak ones. An alternative to the standard reusable password is the one-time password.