There are two different kinds of policies; Standard Policy and Password Policy. Normal policies evaluate to True or False, and can be used everywhere. Password policies apply when a password is set (during user enrollment, recovery or anywhere else). These policies can be used to apply password rules such as length, complexity, etc. They can also be used to expire passwords after a certain amount of time.
passbook keeps track of failed login attempts by source IP and attempted username. These values are saved as scores. Each failed login decreases the score for the client IP as well as the targeted username by 1 (one).
This policy checks the hashed password against the [Have I Been Pwned](https://haveibeenpwned.com/) API. This only sends the first 5 characters of the hashed password. The remaining comparison is done within passbook.