“Your PC may be infected” says Google, which has taken the unusual step of warning users that a couple of million or so of them have most likely been taken in by a fake AV scam. According to a post on the official Google blog by security engineer Damian Menscher, Google has noticed an unusual pattern of user activity. “We found some unusual search traffic while performing routine maintenance on one of our data centers” Menscher explains, adding that they then collaborated with other security engineers at various companies which were sending the modified traffic in question to determine that the machines responsible were infected with a particular strain of malware.

Google decided to warn anyone matching the traffic pattern it has identified (involving the sending of traffic through particular proxies) when making a search by displaying a notification atop of their search results that says “Your computer appears to be infected” and offers advice on how to fix the problem.

The malware in question would appear to be installed when users are taken in by one of up to a hundred different fake antivirus warning scams that have been circulating for the longest time, although Google has so far been unable to actually name the miscreant malware.