Wes Wasson, vice president of marketing at Fort Lauderdale, Fla.-based Citrix, said the acquisition will allow the company to add robust protection for users by incorporating Teros' application firewall appliance to Citrix's Web-based NetScaler application delivery system.

That protection is critical, he said, because Web-based applications can leave a company's critical and private data more vulnerable to hackers. 'The problem is that Web architecture is fairly porous and easy to exploit,' Wasson said. 'Applications link to all of this critical data. It's a perfect storm that has become extremely attractive for hackers.'

Application firewalls differ from traditional firewalls, which only watch for suspicious activities that traverse the network, Wasson said. An application firewall can also watch for and stop attacks beyond the network level in underlying platform layers. And it can fend off attacks that use customized code.

Citrix is immediately rebranding the Teros product as Citrix NetScaler Application Firewall, and over the next year, the company plans to integrate the product into its NetScaler line. Pricing for the application firewall begins at US$45,000 per appliance, and customers usually buy two for redundancy, the company said. NetScaler starts at $17,000 and typically ranges up to a cost of $85,000 per installation.

Financial terms of the deal for five-year-old Sunnyvale, Calif.-based Teros were not released.