Eliot Spitzer, New York state's attorney-general, opened a new front in his attack on internet fraud and other online nuisances yesterday 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. Adware and other types of "spyware" have become a wide-ranging nuisance on the internet, doing everything from delivering unwanted ads to monitoring a computer user's behaviour and stealing information. The complaints have led to a number of industry-led attempts at self-regulation, as well as proposals for legislation in New York and other states that would explicitly outlaw the practice.