Google ads are everywhere. Now they’re being taken to court, too [Video]

One month after a judge declared Google’s search engine an illegal monopoly, the company faces another antitrust lawsuit that threatens to break up the company — this time over its advertising technology.

The U.S. Justice Department, joined by a coalition of states, and Google each made opening statements Monday to a federal judge who will decide whether the firm holds a monopoly over online advertising technology.

The regulators contend that Google built, acquired and maintains a monopoly over the technology that matches online publishers to advertisers. Dominance over the software on both the buy side and the sell side of the transaction enables Google to keep as much as 36 cents on the dollar when it brokers sales between publishers and advertisers, the U.S. government contends in court papers.

They allege that Google also controls the ad exchange market, which matches the buy side to the sell side.

“One monopoly …