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"Update: Twitter is back.  For full coverage of the incident, see previous posts:\n- Twitter Down: Twitter Doesn\u2019t Know Why\n- Facebook Down. Twitter Down. Social Media Meltdown.\nTwitter's extended downtime today, now lasting almost 2 hours, has a malicious cause.  Twitter has revealed that it's defending against a Distributed Denial of Service Attack (DDoS), in which the target is typically saturated with so many fake requests that the victim is unable to return legitimate ones.  \nKnowing that the cause is a malicious attack does take Twitter off the hook to some degree - it may have been assumed that the site was simply failing to scale properly, as had happened in the past.  DDoS attempts are difficult to defend against even for some established sites.  \n\n\nAs to who might have it in for Twitter: the site is so large and visible that the attacker could be anyone...from a lone prankster to a more organized outfit. \nSee also: Twitter down, Facebook down"^^<http://www.w3.org/2001/XMLSchema#string>
<http://mashable.com/2009/08/06/twitter-downtime/>