There are a few different ways; Flash Shared Objects (https://en.wikipedia.org/wiki/Local_shared_object https://en.wikipedia.org/wiki/Local_shared_object ), usi

There are a few different ways; Flash Shared Objects (https://en.wikipedia.org/wiki/Local_shared_object https://en.wikipedia.org/wiki/Local_shared_object ), using Browser + Machine ID information to make sure cookies are linked to the right machine, etc... - see http://samy.pl/evercookie/ http://samy.pl/evercookie/ for a few different other methods