Networking equipment maker Cisco Systems is buying SSL VPN technology company Twingo Systems for US$5 million in cash.

The deal will add Twingo's Virtual Secure Desktop technology to Cisco's VPN 3000 Concentrator product. Cisco said that the new technology will make it easier for Cisco to clean up after SSL (Secure Sockets Layer) VPN (virtual private network) sessions on insecure, remote computers by removing sensitive information stored in temporary files, Web browser caches, cookies and e-mail.

First released in July 2003, the Virtual Secure Desktop creates a virtual desktop on computers using SSL VPN to connect to sensitive corporate networks. Information passed back and forth during the SSL VPN session is stored in encrypted form on the virtual desktop and erased from the machine at the conclusion of the session, according to information obtained from Twingo's Web site.

Privately held Twingo already has deals with other leading SSL VPN makers, including Aventail and Array Networks.

Array announced an OEM relationship with Twingo in January that adds Twingo's technology to Array's unified secure content access products. Aventail and Twingo said in November that Twingo was joining Aventail's Technology Partner Program, ensuring that the Virtual Secure Desktop will work with Aventail's hardware appliances.

After focusing exclusively on IPSec (Internet Protocol Security) VPNs for years, Cisco unveiled its own SSL VPN, called "WebVPN" in November. SSL VPNs are increasingly popular, especially for mobile workers who wish to connect to office networks from airport kiosks or other insecure systems.

As opposed to VPNs that use IPsec, SSL VPNs are typically "clientless," meaning they do not require a separate software application to be installed on the remote user's machine. They also rely on the SSL protocol, which is a part of most common Web servers and Web browsers and widely used to secure e-commerce transactions.

Cisco expects to complete its acquisition of Twingo in the third quarter of its fiscal year, which ends in July. Twingo will be added to Cisco's VPN & Security Business Unit, the company said.