Ubisoft has told Eurogamer that the problems with their DRM servers, that players of Assassin's Creed II and Silent Hunter 5 needs to be connected to at all times in order to play, happened because of outside attacks. The publisher apologized to the people that couldn't play, but said that "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."
"Servers were attacked and while the servers did not go down, service was limited from 2.30pm to 9pm Paris time", Ubisoft said and that "at this time, no valid cracked version of either Silent Hunter 5 or Assassin's Creed II are available." I guess they would say that, either way. And was the word "valid" really a good word for that statement?
Anyway, the DRM service should be up and running now.