In an ongoing fight over ad listings, data company 3Taps has made good on its threat to file an antitrust claim against classified giant Craigslist.

In a claim filed Monday in San Francisco federal court, 3Taps accuses Craigslist of operating as an "unchallenged monopolist" to pull in $100 million to $300 million per year. 3Taps asks the court to declare that Craigslist is violating Section 2 of the Sherman Act, a law that forbids companies from abusing dominant market power.