William Bailey, IT manager at Catholic Charities of Santa Clara County in San Jose, Calif., says he has to block video at the 400-person nonprofit to ensure that the agency's network will remain operational. "It's a real issue when a network can't handle demand, and too much media, particularly video, is usually the reason why," he says. For people like Shawn Birkett, such shutdowns can thwart both legitimate work and extracurricular video-watching. A sales executive with wireless equipment company Moonblink Communications Inc. in Sunnyvale, Calif., Birkett used to spend about an hour and a half a day looking at online video, often related to his company's customers. Then six months ago, Moonblink blocked all Internet video after IT managers found that streaming audio and video had slowed the company's Internet service.

Now, Birkett acknowledges, he doesn't get "sidetracked" by nonwork-related video like he used to. At the same time, the blockage makes it difficult for him to check out clients' online videos. He says he has to call his IT department for special permission each time he wants to view customers' online videos. "It's been frustrating," he says.

Blocking online video isn't easy. As people use the Web for a growing number of capacity-draining functions, from Internet telephone services to peer-to-peer file-sharing, it has become tougher for technology managers to sift through activity on their networks. In addition, the growing use of video as an office tool has made it more difficult to know whether employees are using video sites for work, or for diversion. Stealthy programs like Internet video site Joost NV and peer-to-peer file-sharing service BitTorrent Inc. can cause further problems for IT departments, since the services can confuse network-security measures.

The confusion has created opportunities for small networking companies such as Palo Alto Networks Inc., BlueCoat Systems Inc., SonicWall Inc. and OpenDNS Inc., which offer products and services capable of peering into computer traffic and dissecting it.

Schemmer Associates Inc., an architecture firm in Omaha, Neb., tapped OpenDNS last year to block unwanted video after experiencing substantial network slowdowns. Scott Bennett, network manager for Schemmer, traced the problems to some interns who watched online videos on blogging sites and social-networking portals. In December, Bennett installed the OpenDNS system that categorizes and filters Web content.

Later that same week, the system received its first major test when a 19-year-old high-school dropout shot and killed eight people, including himself, at a shopping mall across the street from Schemmer's offices. During the ordeal, Bennett says Schemmer's employees wanted to watch online news reports but were blocked. Without the new system, says Bennett, the network would have crashed.

"The system saved me from what could have been a huge problem," says Bennett. "I had pretty much the entire office come over and tell me how upset they were at not being able to see reports online. And I told them, it could have been worse."

Meanwhile, R.J. Griffin & Co., a subsidiary of J.E. Dunn Construction Group, says it plans to block employee access to Internet video over the next few months. The 600-person Atlanta company is grappling with the housing downturn and is looking for ways to conserve spending. But the company also wants to add capacity to its existing network. Jason Cunningham, IT director for R.J. Griffin, says blocking video could save the company from making a potentially costly technology upgrade.

Cunningham recently found that YouTube was the most popular Web site visited by R.J. Griffin employees, receiving 3,000 hits a month. To prevent any employee backlash, he plans to issue a report explaining the threat that video poses to bandwidth. He says he dealt with a similar challenge two years ago when the company decided to shut off access to adult-content Web sites after an internal audit found that they were the most widely visited sites at the company.

"I know our people will say we're acting like Big Brother," says Cunningham of the new online-video ban. "But those pipes belong to the company. If management says we need to protect our resources, then that's what happens."