A company official, Marissa Mayer, VP, Search Products & User Experience said each and every search result from between 9:30 a.m. and 10:25 a.m. ET likely resulted' in the message, This site may harm your computer.
This was clearly an error, and we are very sorry for the inconvenience caused to our users, Mayer said.
Google explained the reason for the hiccup, was due to a human error in the list of URLs Google uses to identify and flag websites known to install malicious software. This warning is a result of Google teaming with the site StopBadware.org.
We work with a non-profit called StopBadware.org to get our list of URLs. StopBadware carefully researches each consumer complaint to decide fairly whether that URL belongs on the list. Since each case needs to be individually researched, this list is maintained by humans, not algorithms.
We periodically receive updates to that list and received one such update to release on the site this morning. Unfortunately (and here's the human error), the URL of '/' was mistakenly checked in as a value to the file and '/' expands to all URLs.
The problem has now been acknowledged and fixed by Google.