Twitter, the popular micro-blogging service, was knocked down by a malicious attack that prevented people from accessing its website for several hours on Thursday.
Facebook members saw delays logging in and posting to their online profiles. The social networking site is working with Twitter and Google to determine whether there was foul play, a person familiar with the company said.
The Twitter outage follows a wave of similar cyber attacks in July that disrupted access to several high-profile U.S. and South Korean websites, including the White House site. South Korea's spy agency said at the time that North Korea might have been behind the attacks.
Twitter co-founder Biz Stone said on Twitter's blog that the site was the victim of a denial-of-service attack, a technique in which hackers overwhelm a website's servers with communications requests.
