Twitter under attack, partially online

The popular short-message social networking site Twitter was attacked Thursday morning. The site is partially online, but won't be completely functional for several more hours.

Twitter is back online, just before noon eastern standard time. The site is still operating slower than normal and it could be several hours before the site is fully functional, according to a report on the Fox News Channel. The popular social networking site was not available for several hours Thursday. Twitter is a service where users can share "tweets" about what they are doing, where they are going and other short messages. A post on the Twitter Status blog just before 11 a.m. EST said the site was defending a "denial of service" attack. A post at 10 a.m. EST read "Site is down. We are determining the cause and will provide an update shortly." A "denial of service" attack occurs when multiple systems flood the resources of a targeted site, usually one or more web servers. Hackers use a variety of techniques to compromise these systems. The outage started around 9 a.m. EST, according to CNET.com.