From what I've red I'm legally allowed to modify my personal copy of Ubuntu. Correct me if I am wrong here though.
So my question: I would like to edit how the user logs in. I am using the default 13.10 lightdm. I could not find the login/password text box processing part within lightdm though.
To elaborate on what I am trying to achieve: Take for example that I try to log in as a user 'TEST'. The password for this user is 'MyTestPassword'. I would like to do something when the user enters foe example 'HINT'. As you see, this is not about the appearance of the login screen.
I would appreciate if someone could point me in the direction of the files/ source code that has to be modified.