Twitter Overwhelmed by Web Attack

Update | 12:39 p.m. Added reports that Facebook and LiveJournal are also experiencing major system problems.

Update | 1:39 p.m. Added confirmation of problems at Facebook and LiveJournal.

Twitter, the popular microblogging service, was crippled Thursday morning by a denial-of-service attack.

The extended silence in a normally noisy Twitterworld began around 9 a.m. Twitter later posted a note to its status update page saying the site had been slowed to a standstill by an attack. In a denial-of-service attack, hackers typically direct a “botnet,” often made up of thousands of malware-infected home PCs, toward a target site in an effort to flood it with junk traffic. With the site overwhelmed, legitimate visitors cannot access the service.

“On this otherwise happy Thursday morning, Twitter is the target of a denial-of-service attack. Attacks such as this are malicious efforts orchestrated to disrupt and make unavailable services such as online banks, credit card payment gateways, and in this case, Twitter for intended customers or users,” co-founder Biz Stone said in a blog post. “We are defending against this attack now and will continue to update our status blog as we continue to defend and later investigate.”

At about 11 a.m., Twitter updated its status site with a note saying, “The site is back up, but we are continuing to defend against and recover from this attack.”

However, many visitors are still finding the site inaccessible. (What’s your experience? Let us know in the comments.)

Other sites reported that they were targets of denial-of-service attacks as well. The social-networking site Facebook said access to its site was impaired for some users for a short time Thursday morning. It said it had mostly resolved the problem but was continuing to monitor the situation. “No user data was at risk and we have restored full access to the site for most users,” a Facebook statement said.

LiveJournal said it, too, sustained a denial-of-service attack. The assault also began at about 9 a.m., and site access was limited for about an hour. It is unclear whether the problems at the sites are connected.

Twitter has contended with a series of security woes recently, including the hacking of several employees’ e-mail accounts and theft of company documents as well as a surge of phishing, spam and other malicious attacks aimed at its users. It reportedly has been undertaking a top-to-bottom security review.

The Web sites operated by Gawker Media were the target of a similar attack earlier this week.

By Riva Richmond