Google's acquisition spree shows no signs of stopping: now the company has acquired Mountain View-based GreenBorder, which creates security software. It's an interesting idea: the software creates a kind of sandbox for your web browsing, so that any viruses, spyware and trojans you pick up during your session are deleted as soon as the browser is closed. The name comes from the green border applied to your browser window when the service is active, letting you know that the whole session is being contained and no changes will be made to your PC by websites (even downloads are opened in a virtual environment).

In their own words, GreenBorder has created an "easy solution to virus, spyware, and trojan threats by isolating each Internet session from the rest of the PC and earlier Internet sessions. The beauty of the GreenBorder Pro software is it doesn't need to be updated to guard against new virus signatures or new types of malware. It creates a secluded, virtual Internet session and when you are done, it flushes everything away, in your cache and in temporary files." GreenBorder Pro costs $29.95, but will most certainly become free now that Google is in charge.

The question is: does this mark Google's first step into the security and anti-virus game? It's an area of web browsing that Google hasn't yet ventured into, but the company's relentless march would seem to put it in competition with virtually everyone.