Hollywood stars are launching an attack on Internet sites that make money by showing fake or stolen nude pictures of celebrities. Alyssa Milano (25) an actress from the long-running soap Melrose Place, filed two lawsuits in Los Angeles on Tuesday against several sites she says show pictures of her naked.

The action is the first of its kind and is regarded as a test case against a growing industry exploiting digitalised nude images that are often flagrant violations of copyright or outright fraud.

Milano's Beverly Hills lawyer, Michell Kamark, said: "Celebrities are realising for the first time that the Net is a dangerous force if it's not corralled."

One of the defendants named by the actress is John Lindgren (21), who claims to make around $10,000 a month from his Website, nudecelebrity.com, run from Minnesota.

Rather than going to the expense of defending himself he said he would remove the Milano pictures but would continue the business using other stars' pictures.

Many of the pictures are made by grafting the head of a star on to a nude photo of someone else. A gallery of nude images can be created using relatively simple desktop publishing equipment.

Taking pictures from a film is trickier and a direct infringement of copyright. Some pictures are copies of paparazzi shots.

The sites make money by charging access fees, selling the pictures on-line for about $100, or making more elaborate and expensive CD-Roms with hundreds of pictures. Customers give a credit card number and another company which checks their veracity will also verify that the buyer is not a minor, one of the few legal requirements in the burgeoning Internet porn business.

Although the law is mainly in Hollywood's favour, closing down the electronic peep-shows is probably impossible. The Internet is almost completely unregulated and the astonishing proliferation of pornography in cyberspace is testament to the genre's popularity.