Today, AVG announced the acquisition of Sana Security, a longtime host-intrusion prevention software vendor. I have particular affection for Sana because they were a former client of mine at a previous job. Back in the summer of 2007, when security startup venture money was still flowing freely, like a rose-scented fountain at a Vegas casino, I remember giving a speech for Sana at their San Jose Grand Prix event. Don Listwin, their then-CEO, was a serious car racing enthusiast. He had conspired with the city of San Jose to shut down the city center so they could run race cars down the middle of it. It was pretty wild stuff -- speaking as someone who comes from Boston, where all of the roads seem to be derived from old horse-trails or giant spiderweb patterns.

Host intrusion prevention software has always been a fascinating subsegment of client security, not least because of the fact that what HIPS vendors try to do is actually pretty hard stuff. In concept, the idea sounds simple: monitor processes in memory for suspicious activity, and block them when they try to do something naughty. For example, an ActiveX control executing in the context of a website should not be allowed to open a command shell and then initiate an outbound connection to somewhere else. Simple, right?