Ubisoft has blamed problems with its controversial digital rights management solution for PC games on outside attacks.
The publisher told Eurogamer that very few players were unable to access PC versions of Assassin's Creed II and Silent Hunter 5 yesterday due to the outage, but apologised to those who did experience problems.
"Ubisoft would like to apologise to anyone who could not play ACII or SH5 yesterday," the company said in a statement this afternoon.
"Servers were attacked and while the servers did not go down, service was limited from 2.30pm to 9pm Paris time [1.30pm - 8pm GMT].
"95 per cent of players were not affected, but a small group of players attempting to open a game session did receive denial of service errors.
"All players with an open session during the attack were not affected.
"We also confirm that, at this time, no valid cracked version of either Silent Hunter 5 or Assassinís Creed II are available."
Ubisoft's DRM system requires players to be online at all times while playing PC versions of its games.
There are benefits to the service - cloud storage of save-games, the ability to install and play from multiple locations - but the publisher has come under fire from PC gamers who resent the security measures and worry about being booted out of software they paid for if the internet goes down.