Twitter went offline overnight, after a hack attack by a group of Iranian protesters re-directed the site's DNS to a protest page.
Because of the attack, users of Twitter were unable to log on to the site for a number of hours, meaning around 30 million people were unable to post their 140 character missives online.
The site's interface was replaced by a protest sign, which explained: "This site has been hacked by the Iranian Cyber Army.
"The USA thinks they control and manage internet access, but they don't. We control and manage the internet with our power, so do not try to the incite Iranian people."
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Twitter eventually posted a short statement on its blog, explaining: "Twitter's DNS records were temporarily compromised but have now been fixed.
"We are looking into the underlying cause and will update with more information soon."
This isn't the first time the site has been the subject of hackers, back in August the site was the subject of a DDoS attack.