UBTU-16-010240 - Passwords must have a minimum of 15-characters.
The shorter the password, the lower the number of possible combinations that need to be tested before the password is compromised. Password complexity, or strength, is a measure of the effectiveness of a password in resisting attempts at guessing and brute-force attacks. Password length is one factor of several that helps to determine strength and how long it takes to crack a password. Use of more characters in a password helps to exponentially increase the time and/or resources required to compromise the password.
Configure the Ubuntu operating system to enforce a minimum 15-character password length. Add or update the following line in the '/etc/security/pwquality.conf' file or a configuration file in the /etc/pwquality.conf.d/ directory to contain the 'minlen' parameter: minlen=15