Social networking site Twitter rolled back to a previous version of its website following an outage that left users unable to access the site.
In a blog post, Mazen Rawashdeh, vice president of engineering at Twitter, downplayed suggestions the site was hacked and said the outage was caused by a "cascading" bug.
This wasn't due to a hack or our new office or Euro 2012 or GIF avatars, as some have speculated.
However, at least one hacker group claimed responsibility for the downtime.
UgNazi, a relatively new group on the hacking scene and loosely affiliated with Lulzsec, said it launched a Distributed Denial of Service (DDoS) attack against Twitter over the company's support for the Cyber Intelligence Sharing and Protection Act.
Rawashdeh said the fault was discovered at 9am Pacific Time yesterday. "We discovered that Twitter was inaccessible for all web users, and mobile clients were not showing new Tweets," he said.
He said engineers began investigations into the downtime and found there was a "cascading bug in one of our infrastructure components."
"This wasn't due to a hack or our new office or Euro 2012 or GIF avatars, as some have speculated today," said Rawashdeh.
A cascading bug is one with an effect that isn't confined to a particular software element, he explained.
"One of the characteristics of such a bug is that it can have a significant impact on all users, worldwide, which was the case today.
"As soon as we discovered it, we took corrective actions, which included rolling back to a previous stable version of Twitter," he said.
He apologised for the outage and noted that in the past six months, Twitter had an up time of at least 99.96 per cent and often 99.99 per cent.
"This means that in an average 24-hour period, twitter.com has been stable and available to everyone for roughly 23 hours, 59 minutes and 40-ish seconds. Not today though," he joked.
