Internet service providers, Web site operators, and manufacturers of devices that are used by some to pirate content should play a part in stamping out that piracy, Sumner Redstone, chairman and controlling shareholder of both Viacom and CBS, said. "It is obviously impossible to check every computer or look over the shoulder of every user around the world to see whether they have a license to use our content -- and we don’t want to do that," said Redstone in a keynote address to the Seoul Digital Forum, which was monitored by Web cast in Tokyo.