Analog form -- illegal tape recordings -- acknowledged its growing new digital problem quite loudly last week, filing three lawsuits against the operators of Web sites reportedly pirating and distributing copyrighted songs free over the Internet.

"We are serving notice to other sites that we are going to vigorously protect our copyrights," said Hilary Rosen, the president of the Recording Industry Association of America, which filed the suit on behalf of its members. Because the names of the Web site operators were unknown, the industry sued the Internet addresses, hoping to discover who the operators actually were.

"Other owners of intellectual property -- the recording industry, the movie industry, the photo people -- are finding themselves with the same problem the software industry has had for years," said Bob Kruger, vice president of piracy enforcement for the Business Software Alliance in Washington.

Now that most music is available in a digital format, hackers and music fans alike can easily post songs on the Internet. No matter how many times they are copied, the quality of the sound remains consistent and the song remains consistently free. "The recording industry has always been able to protect itself through the argument that there is a degradation in quality from one generation to the next," Mr. Kruger said. "But now there is absolutely no difference between the original and the copy -- you have removed the disadvantage."

Most of the "virtual" bootleggers who operate Web sites that offer illegal music copies do it as a hobby, not to make money, according to those familiar with such cases.

"He did not think he was violating the law," said Andrew Dickey, president of BestWeb, an Internet service provider that was host to the Web site of an unidentified 19 year old male, whose site was sued by the recording industry.

"They view this as a victimless crime," Mr. Kruger said. "They don't understand the scope of the threat they pose to the industry."