As of yesterday... google can now detect if your PC has a particuliar type of malware infection when you execute a search on http://www.google.com. If your PC is infected you'll get a yellow bar like in the image below.
Personally, I think this is genius. Too many people don't check their machines or stay up to date with proper malware/virus scanning tools. If popular websites integrated a scanning services I think it could potentially cripple botnets. Of course, this first attempt is to block a particuliarly bit of malware, but I think the idea is a good one.
The Internet brings remarkable benefits to society. Unfortunately, some people use it for harm and their own gain at the expense of others. We believe in the power of the web and information, and we work every day to detect potential abuse of our services and ward off attacks.Read more at googleblog.blogspot.com
As we work to protect our users and their information, we sometimes discover unusual patterns of activity. Recently, we found some unusual search traffic while performing routine maintenance on one of our data centers. After collaborating with security engineers at several companies that were sending this modified traffic, we determined that the computers exhibiting this behavior were infected with a particular strain of malicious software, or “malware.” As a result of this discovery, today some people will see a prominent notification at the top of their Google web search results: