The US government's complaint that it closed the KickassTorrents and led to the arrest of Artem Vaulin, shows us how one can work system detection.
Here it would be good before we start blaming it Facebook and Apple to examine the responsibilities of the owner of the website KickasssTorrents. Using a personal email address on Facebook might sound like a completely innocent thing to you, but in Vaulin's case it was really stupid.
How personal? It was a "@ me.com" address, a domain owned by Apple (forerunner @ icloud.com).
His address was discovered when authorities sent a Facebook warrant for information related to the site's site. From there, the US government headed to Apple.
Vaulin used the same @ me.com email to make a purchase from iTunes, so his IP address was recorded by Apple that collects information from each transaction. IP addresses can also be linked to bitcoin accounts.
Apple and Facebook did not do anything different and seem to have acted within the legal limits by providing information following the government's warrants. For big companies this is really routine really.
But the fact that Vaulin used a single, personal email address post officey in so many services and features it's incredible. If someone is trying to hide and uses an address linked to something as personal as their Apple ID, they're living in a different world.
It should be noted that at the time of his arrest, Vaulin was not known to be the owner of KickassTorrents - or the "alleged" mastermind. But there is ample evidence that he is probably the only one responsible for KicKassTorrents.