Pornography and other Internet content that company bosses find objectionable is increasingly getting blocked on corporate networks. Systems that prevent employees from visiting sites that a company deems off-limits are fast becoming a standard part of business networks. In fact, IDC estimates the market will be worth $636m by 2004. The newest entry in the rapidly maturing product category is Telemate.Net Software, which next month plans to ship the industry's first site-blocking system built as a high-performance, turnkey network device. Until now, Web-blocking products aimed at businesses -- such as those from Elron Software, SurfControl and Websense -- have been available only as software. Telemate.Net's NetSpective WebFilter appliance, which passively "sniffs" Internet traffic until it detects a forbidden site, can handle a fully saturated 100Mbps network link, according to the company. In internal testing, Telemate.Net said, the box stood up to 40,000 simulated users continuously accessing Web pages. "The network managers we talked to did not want something that would bring the network down," said Vijay Balakrishnan, senior vice president of marketing at Telemate.Net. The company will sell NetSpective WebFilter as a subscription, starting at $3,995 (£2,799) per year for 250 employees. Arrowhead Products, an aircraft parts company in California, has been testing the beta version of Telemate.Net's NetSpective WebFilter appliance for several weeks. The first week it was in operation, Larry Wible, Arrowhead's information systems project manager, was surprised to find that about 70 percent of all Internet traffic was going to sites that were not work-related. Wible said a longtime Arrowhead employee was recently fired for surfing porn sites at work. "What we're trying to do is avoid that happening in the first place," he said. The NetSpective WebFilter appliance automates the process of figuring out which sites to block, based on the context of the page, rather than relying exclusively on human editors. When an employee visits a site that the NetSpective WebFilter hasn't categorised, the device sends the URL to Telemate.Net's data centre. Using software licensed from RuleSpace, Telemate.Net analyses the site and places it into a category. The site is then checked by a human to make sure it's in the right place, and the updated site category is then sent back to the customer's NetSpective WebFilter appliance. They can see you... Read about how and why in Surveillance, a ZDNet News Special Take me to ZDNet Enterprise Have your say instantly, and see what others have said. Click on the TalkBack button and go to the ZDNet News forum. Let the editors know what you think in the Mailroom. And read what others have said.