Alexandria: Google faces a fresh federal court test on Monday as US government lawyers ask a judge to order the breakup of the search engine giant's ad technology business. Monday's case focuses specifically on Google's ad tech "stack" -- the tools that website publishers use to sell ads and that advertisers use to buy them. According to filings, the US government will argue that Google should spin off its ad publisher and exchange operations. This remedy phase of the US trial follows a first trial that found Google operated an illegal monopoly. Instead of a major breakup of its business, Google was required to share data with rivals as part of its remedies.