Ubisoft has revealed that the downtime of its DRM servers over the weekend was caused by an attack, making it difficult for gamers to play both Assassin's Creed II and Silent Hunter 5 on PC.

"Apologies to anyone who couldn't play ACII or SH5 yesterday," said the publisher in a tweet. "Servers were attacked which limited service from 2:30pm to 9pm Paris time."

Earlier Ubisoft said the server was having difficulty coping with "exceptional demand".

Given the widespread negativity of Ubisoft's latest DRM policy - requiring users to authenticate the game over the internet - it wouldn't come as a surprise if the attack was orchestrated by members of the PC gaming community in protest.