Which is why this flashcart is saying "don't go online unless you're using your own backups". This cart spoofs the unique signature and such to the console. If you download mario kart 8 from a torrent and run it here, you'll trip Nintendo's copy detection. If you go to a gamestop and buy a used mario kart 8, then back it up to this thing and return the cart to the gamestop... Well one of two things happens.

1: Nintendo's system is manually managed and Nintendo checks cartridge certs against a known dataset of pirated copies. You can now play pirated Mk8 online because of your valid cert that doesn't match any known dumps.

2: Nintendo's system is automated and will permanently ban anyone online with a given cert in two consoles at once. You can now play pirated Mk8 online until someone else goes to the gamestop, buys the cart you used, and tries to play online at the same time as you. Now you and the guy that bought the used game are perma'd.

I guess they learned a lesson from R4... So, they just need to have a DB of IDs tied to IPs. If an ID starts repeating a lot with different IPs (distributed around the world), they can clearly block at will. These kind of developments may be difficult to keep alive, then. Well, caveat emptor, I guess.