[t0mas88]

In my European country the law very specifically tells ISPs what to record. It doesn't require them to produce any conclusions or other data, so if you ask for a subscriber name without enough details (port and destination in this example) the response I gave is totally legal. I have in fact seen that kind of thing happen and compliance departments tend to favor exactly this, do what the letter of the law said, not a byte more unless a court orders them. The risk otherwise is that you're illegally violating the privacy of a customer just to please some law enforcement agency.

As a follow-up the agency, with the right court order, could get all the raw connection records and try to figure it out themselves. But if you don't know the exact time and (source IP, port, destination IP, port) combination you're not going to figure it out in a network with large scale NAT.