Mi5 Networks, which makes a Web security appliance, will be integrated into Symantec's product line later this year.Symantec announced Monday it is acquiring Mi5 Networks, which makes a Web security gateway appliance.

Mi5 is one of the winners of our first-ever Startup 50, which recognizes 50 innovative young companies building products for enterprise IT.

Mi5's Web appliance can be stocked with modules for URL filtering and malware detection. On the malware detection front, it prevents users from going to known spyware sites, and will inspect active content such as ActiveX and Java for malicious attributes. It also scans file downloads and will stop users from downloading infected files.

It can also detect and block attempts by malware on PCs to "phone home" to a control system. The company also offers an ActiveX agent that can be deployed from the appliance to infected PCs to clean up viruses and spyware.

Mi5 currently uses the Sophos antivirus engine. Symantec says it will replace Sophos with its own AV technology.

Mi5 was founded in 2004 by Doug Camplejohn and Ofer Doitel. The company had raised $4 million in venture capital from Labrador Ventures and First Round Ventures.

The acquisition closes a hole in Symantec's portfolio, but it faces strong competition. Websense leads the market in Web security gateways. Other competitors include McAfee (via its acquisition of Secure Computing's Web Washer) and IBM ISS.