The longer a password is, the longer it takes for a computer to enter every possible letter combination. Make the phrase at least 16 characters for a comfortable amount of security.
Cyber Security Awareness
Cyber Tip: Password Security
Passphrases allow you to use natural language. Making it easier to remember and type. While using 16+ characters gives it the length which is harder for computers to break. For example, IloveourAUEagles! AU Policy doesn't require symbols, they are optional and can be used for fun.
As a failsafe, don't use the same password for all your accounts. If one of your passwords gets stolen, your information is not completely compromised. A password manager is a helpful tool for keeping track of them all.