Requiring that passwords conform to rules of length, complexity, and unpredictability increases the likelihood of someone gaining unauthorized access to a user' s account  Since most user accounts are automatically locked after a certain number of incorrect password guesses, it is usually impossible to gain access by guessing a password
However, because complex passwords can be hard to remember, users often write them down
When a password is written down, it increases the chances that someone will be able to use that password to gain unauthorized access to the user 's account.