|  |  | Strong passwords are essential to our network systems. Cisco devices, which tend to be located at the entry points to our networks, affect entire networks instead of just one system. Many password-cracking tools attempt to guess passwords by matching them with a dictionary. Passwords that aren't in Webster's Dictionary, however, can also be cracked. The best passwords use three of the four cases of characters: lower case, upper case, numbers, and special characters. Passwords may also contain the first letters of each word in a phrase that a user can remember.