A US federal judge has ruled that Google unlawfully exploited its dominance in the search and advertising markets, marking a significant victory for the US Department of Justice's antitrust efforts. Judge Amit Mehta deemed Google a monopolist, violating antitrust laws by making illegal deals to be the default search engine on devices like Apple's. This ruling opens the door for its competitor, Microsoft, which sees potential in replacing Google as Apple's default search provider, a move that could cost Microsoft up to $15 billion annually. Google acknowledges the ruling but plans to appeal, arguing that the court recognized its search engine as superior while wrongly restricting its availability. Meanwhile, Apple is preparing for potential impacts on its revenue from Google by pivoting towards artificial intelligence and revamping its Siri assistant to mitigate losses. The case's outcome raises questions about the future of search engine competition and regulatory measures in the tech industry.