End user copyright infringement is about as low a priority for legal firms/in house legal types as can be. Beyond that they have to detect it and go after people, the main way anybody used to get detected was p2p services (mostly torrents but the gnutella family had stuff as well) would have the IP addresses of the people sending and receiving and then they would use various laws to get the info and send people either a warning letter, try to shake them down (pay 200 now or see us in court) or get their ISP to send a letter. There are ways to mitigate this, the most ineffective being peerblock/peerguardian and it then going through things like proxies, VPN and seedboxes...
I have no idea what that iso site is and thus no idea how they work. However if they do not do torrents and such then it gets somewhat harder to track people here (not impossible -- you get a court order to take over the service, maybe something if they use a CDN...). Games tend not to be the highest priority for people that would go after things here, though there have been some interesting cases from games (the pay us or court stuff happened for I think it was a rally game once).