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Twitter taken down by nasty 'cascaded' bug

Service was spotty for Twitter users as the company scrambled to figure out why the site was down. While Twitter says it's an internal issue, a hacker group is claiming responsibility.

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It was a confusing day in the Twittersphere as users were met with a spotty site service outage this morning. The service went down and up multiple times in a two-hour period beginning around 9 a.m. PT.

Twitter said the outage's cause wasn't an attack, but a failure within Twitter's system. The company said it was a "cascading bug," which sounds like a bug caused a domino effect on the system.

Twitter's VP of engineering Mazen Rawashdeh wrote in a blog post today that the bug isn't confined to a particular software element and instead "cascades" into other elements, affecting users worldwide. He said the company took "corrective actions" after it discovered the bug.

"Not how we wanted today to go. At approximately 9:00am PDT, we discovered that Twitter was inaccessible for all web users, and mobile clients were not showing new Tweets. We immediately began to investigate the issue and found that 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," he wrote.

And while the company said it was not under attack, hacker group UGNazi tried to claim credit, CBS Atlanta reported.

Hacker Hannah Sweet, known as "Cosmo" and @CosmoTheGod on Twitter, said UGNazi took Twitter down for 40 minutes worldwide with a "distributed denial of service" attack and the hackers are continuing to do so.

Sweet said that the group attacked Twitter because of the site's support of Cyber Intelligence Sharing and Protection Act (CISPA), a bill that allows the federal government and private businesses to share information about possible cyber threats.

Twitter appeared to be completely down starting 9 a.m. PT, according to monitoring site Pingdom. According to the stats on Pingdom, this looks to be Twitter's worst crash in months.

After Twitter said its service was back up mid-morning following about an hour of service interruption, the site went down again. Rawashdeh wrote that recovery begain around 10:10 a.m. PT and then began full recovery at 11:08 a.m.

"Update: The issue is on-going and engineers are working to resolve it," the company's blog status read at 10:57 a.m. The site's service continued to yo-yo into the afternoon.

"We are currently conducting a comprehensive review to ensure that we can avoid this chain of events in the future," Rawashdeh wrote, adding that Twitter was at its highest marks for site reliability and stability in the past six months.

Update, 2:57 p.m. PT: Updated with information from Twitter.