Eliot Spitzer, New York state's attorney-general, opened a new front in his attack on internet fraud and other online nuisances on Thursday with a lawsuit against one of the biggest US producers of adware.

The case accuses Intermix Media, a Los Angeles-based internet marketing company, of planting software on consumers' computers without their knowledge, allowing the company to deliver pop-up ads or hijacking internet users' attention to its own sites.