Popular Sites Blocked by Web Attack: Report
Close up of someone typing on a laptop.

Several Web sites including were temporarily down for many who logged on to find error messages and slower navigation after a company that provides directory services for the sites suffered a denial of service attack, according to the Wall Street Journal.

Neustar, whose service helps link individual computers and Web sites, told the newspaper that the disruption lasted for about an hour and only affected people in Northern California.

A denial of service attack typically happens when a group of people use multiple computers to flood a Web site with traffic.

Neustar is still investigating the attack, according to the Wall Street Journal.