Twitter confirmed today that it’s currently defending itself against a malicious DDoS attack, resulting in the social networking site to go offline for a few hours.

A DDoS attack is a distributed denial-of-service attack which essentially floods the target’s web servers with so many requests that it causes delays or failed requests when trying to visit the website. The attacks can be carried out with by an individual or by organised ‘cyber gangs’ using many servers to increase the severity.

There have also been reports of Facebook going down today, but at the moment there doesn’t seem to be a connection between the two issues.

07/08/09 Update - The attack now seems to have escalated and has now affected other large sites like Google and Live Journal (as well as Facebook as I mentioned yesterday) in what is being described as a "massively co-ordinated attack". Reports are suggesting the attack is being targeted towards a single Internet user (who has accounts on all affected websites) to force his silence over the 2008 South Ossetia war between Russia and Georgia, which broke out exactly a year ago today.