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 Schneier aptly puts it,
There’s a lot that Google sees as a result of it’s unique and prominent position in the Internet. Some of it is going to be stuff they never considered. And while they use a lot of it to make money, it’s good of them to give this one back to the Internet users.
The comments on Scheier’s article are worth reading for all security enthusiasts.