How does the Facebook Like button work?

How does the Facebook Like button work?

I want to provide a simple piece of Javascript (or an iframe, I guess) that allows 3rd parties to embed functionality from my site in theirs. The user of said widget will be authenticated on our site already - so basically the Facebook Like button, or Facebook Connect, are the closest examples I could find.
Since Facebook has a few different buttons I'm struggling to understand exactly what they're doing though. Is there a succinct (and technical - I'm a developer and want to build my own widget) explanation somewhere? I'm particularly focused on the security issues involved.


Answer 1:

Here is a brief explanation of the facebook ‘like’ button and here is a tutorial on how to build a web widget. Finally here is a discussion on the security of web widgets.

Answer 2:

I believe the Like button is using cookies to obtain your FB user information, that with additional attributes are then sent to a service endpoint.

As for security measures, an obvious would be to allow requests only from websites with given access keys.