Writing a plugin to intercept a login?

Hi there,

can anyone help?

I would like to write a service to intercept a login form a user, I have taken a look at the “userService” and i do know java pretty well.

But i am unsure how to intercept something.

What i would like to do is when someone logs in/ connects i would like to launch a listener so i can do some custom code.

Any ideas or help woudl be really appreciated.

Thanks