Twitter Goes Down Briefly After Another Cyberattack

Twitter, the Web site that lets people post updates through 140-character messages, said it was attacked again by hackers, following a series of assaults that hobbled the site last week.

"We're back up and analyzing the traffic data to determine the nature of this attack," San Francisco-based Twitter said Tuesday on its blog.

Twitter was the target of a denial-of-service attack last week, along with Facebook and LiveJournal. Hackers targeted an activist blogger from the former Soviet republic of Georgia by flooding the sites with requests, causing them to slow down or crash.

"Twitter continues improving system response such that inevitable denial-of-service attacks such as those we saw last week don't interfere with normal operations," Twitter said in a statement. "We make every effort to keep folks updated."

The company said last week that defense measures caused some of the disruptions. The site was shut down entirely Aug. 6. The next day, many users could not send updates, known as Tweets, via short messaging service and other applications, Twitter said.

Twitter had 20.1 million U.S. users in June, according to research firm ComScore in Reston. That made it the third most popular social-networking site. Facebook and News Corp.'s MySpace ranked first and second.