Thousands of gamers have been barred from playing Xbox Live by Microsoft in an attempt to clamp down on piracy. The US computing giant said it had banned consoles because owners had modified the equipment to play games without paying for them. People whose Xboxes have been blocked will have to buy new machines if they want to connect to Xbox Live. The internet service allows the 20 million gamers signed up to compete against each other via the web. Fans of Microsoft's Xbox system can still play games off-line if their console has been blocked from Xbox Live. The company would not say exactly how many customers were affected although reports suggested the number could be as high as one million.