Social networking sites Facebook and Twitter were crippled yesterday after being targeted by internet hackers.

Twitter was the worst affected by the Denial of Service (DOS) attack, which struck at around 1400BST, taking the site completely offline. Twitter reappeared around three hours later but at present, the service is still struggling to get back to full operation.

A series of updates have been posted by Twitter on a temporary blog, with the site claiming “We are defending against a denial-of-service attack, and will update status again shortly.” Further updates were issued throughout the day and although the site is accessible, Twitter’s API clients (who provide services based on or around Twitter) such as Tweetdeck and Hootsuite are still experiencing problems.

“Attacks such as this are malicious efforts orchestrated to disrupt and make unavailable services such as online banks, credit card payment gateways, and in this case, Twitter for intended customers or users,” said Twitter co-founder Biz Stone on the company’s blog.

Facebook, which was also targeted, said its service was reduced but was not taken offline.

“No user data was at risk and we have restored full access to the site for most users,” Facebook spokeswoman Brandee Barker told the AFP news agency.

“We’re continuing to monitor the situation to ensure that users have the fast and reliable experience they’ve come to expect from Facebook.”

It’s believed that the attack could have affected nearly 300 million people, with Facebook boasting 250m users in addition to Twitter’s 45m.

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