Attack on Twitter silences Tweeters

Twitter, the fast-growing social media for trading short messages, suffered a prolonged attack Thursday, knocking the service out for hours in the morning and resulting in slow and intermittent service later in the day.

The company said it was the victim of a “distributed denial of service,” or DDOS, attack, a disruptive tactic in which outsiders attempt to overload a Web site with huge numbers of computer-generated requests – even, for instance, to refresh a Web page.

Because sites have a limited capacity to handle such requests, a deliberate deluge can cause servers to respond slowly to legitimate users or not at all.

“It basically just shows that Twitter wasn’t spending the money to filter out DDOS attacks,” said John Pescatore, a security analyst at research company Gartner.

Because Twitter is a consumer-oriented site, he said, it’s common that such sites learn the hard way because they “don’t invest in the reliability and the protection against threats that a business-grade service does.”

Twitter’s traffic and membership have exploded in the past year, rocketing to more than 20 million unique visitors in June from 600,000 a year earlier, according to Web ratings company ComScore Inc. Nielsen’s Web ratings service said Twitter reached nearly 10 percent of online users in June.

Twitter came partially back online later in the day, but users reported spotty performance and many said they could not access the service on mobile devices such as iPhones and BlackBerrys.

Facebook was also the subject of a denial-of-service attack Thursday, though it was not known whether the same hackers were involved, but Facebook never became completely inaccessible.