Spring Security and Authentication Changes

[Xephonic]

I'm rather new to all this and i was hoping somebody might be able to point me in the right direction. I'm currently working on a project that uses Spring Security for user/password authentication, but I was wondering if it /where it is possible to override or extend in order to have it so if another condition of my choosing is met, the login does not go through as valid despite a proper username and pass? Would i just need a custom authenticationmanager and implement authenticate or do i need to look elsewhere?
Thanks