According to numerous reports, all web searches did through Google on January 31 between 6:30 AM and 7:30 AM PST returned fairly unexpected results. It seems that all the web sites displayed in the results page were labeled as potentially malicious and users were prevented from accessing them.

During this time interval, when a web site was accessed through a Google search, users were displayed a warning message, telling them that the URL has been identified as containing malicious code. The warning page displayed the URL that had to be copied and pasted in the address bar in order to proceed to that web site. Ironically, though, even Google’s own web addresses were labeled as malicious.

The error was soon addressed and Marissa Mayer wrote a post on the official Google blog in order to clarify the situation. According to the blog post, an employee that was working on the index of the URL blacklist caused the error. It seems that he wrongly inserted an URL containing the “/” character and thus, he labeled all the websites contained by Google’s index as containing malware.

Mayer stressed that the error has been quickly corrected, so no user has been affected for more than 30 or 40 minutes. The Google vice president apologized for the mistake and reassured users that developers would update and improve the database in order to prevent this kind of errors to reappear.

Google is collaborating with Internet watchdog StopBadware.org in order to index malware web sites. Usually, potentially dangerous websites are specifically labeled in web searches that include them in the results.