Even as much of the Internet has come to resemble a pleasant, well-policed suburb, a little-known neighborhood known as Internet Relay Chat remains the Wild West. While copyright holders and law enforcement agencies take aim at their adversaries on Web sites and peer-to-peer file-sharing networks like Napster, I.R.C. remains the place where people with something to hide go to do business. Probably no more than 500,000 people are using I.R.C. worldwide at any time, and many of them are engaged in legitimate activities, network administrators say. Yet that pirated copy of Microsoft Office or Norton Utilities that turns up on a home-burned CD-ROM may well have originated on I.R.C. And the Internet viruses and "denial of service"" attacks that periodically make news generally get their start there, too. This week, the network"s chat rooms were abuzz with what seemed like informed chatter about the Sasser worm, which infected hundreds of thousands of computers over the weekend.