Joomla User creation hooks

Is it possible to create a hook when a user creates an account?

I have googled and found some stuff on hooks and joomla but nothing really concrete.

Anyone knows if this is possible? Or do I really have to mess with the code. I just want to create code that is upgrade safe.

Thanks

Yes, this is possible. You're going to write an user plugin based on user events for plugin system. From your question I believe you want onAfterStoreUser or onBeforeStoreUser event hooks. Check these provided links for official documentation with examples.