A security tool that identifies botnets and blocks attacks from these zombie networks is being made available by Trend Micro online in the software-as-a-service model.

The Botnet Identification Service, one of three hosted security applications that are part of Trend Micro's SecureCloud line, deals with the growing botnet problem with real-time identification of command and control centers that operate zombie networks. The product is targeted at ISPs and educational institutions.

"The information enables customers to block communications between these [command and control centers] and the compromised PCs they control," Trend Micro states. "By breaking the communication cycle, the botnets are rendered harmless without affecting other services."

This prevents malicious activity even though a computer may still be infected, says John Maddison, general manager of network security for Trend Micro.

Botnets are networks of infected computers controlled remotely by hackers who use them to distribute spam and viruses. About 200,000 new zombie computers are identified each day by the vendor Secure Computing, which also offers technology to track zombies and block the messages they send. Federal investigators have identified more than 1 million botnet crime victims.

IT administrators often don't realize they have zombie machines on their networks. You can find out if suspicious e-mail is originating from your network by clicking on this link on the Secure Computing Web site.

Trend Micro's Botnet Identification Service costs 9 cents per user for as many as 500,000 users.

Trend Micro has two other hosted security services: Interscan Hosted Messaging Security, an e-mail security service that protects against viruses, spam, malware, phishing and other threats; and Email Reputation Services, which allows network administrators to change the sensitivity of e-mail address blocking.

These two services are typically packaged. InterScan Hosted Messaging Security costs US$28.50 per user for up to 250 users, while Email Reputation Services costs $6.80 per user for up to 250 users.

Maddison touted the ability of hosted security services to provide lightning-quick updates.

"One of the biggest benefits is we're able to update our systems very fast," he says. "There's a lot of PDF spam right now hitting customers. It's very hard even if you can find the pattern with that particular PDF spam. We can process that quickly. As soon as you do that update, all 6,000 customers [who use the Email Reputation Services] are updated instantaneously."