FB Like jacking question

[PhilW]

Hi!

I have heard that most like jacking scripts (those which have an invisible Like-button underneath the cursor) stop working very quickly.
Why do they stop working? Most likely because Facebook somehow noticed that something is "off". But how do they notice it? Do they somehow recognize the javascript code of the like jacking script? Then why shouldn't it be possible to somehow hide that code from facebook?
Or is it something different?

Thanks!
Phil

PS: Does someone know a (free) like jacking script that actually works? (as long as Facebook doesn't get wind of me using it) I have to admit that I don't feel like trying dozens of script until I find a working one.
PPS: I hope this is the right forum. Like jacking is not exactly whitehat, but this is the only subforum about social media.