Twitter suffered four separate computer worm attacks over the Easter weekend - with a 17-year-old student claiming responsibility for starting it all.
Co-founder Biz Stone said on the official Twitter blog that a self-replicating computer program had been introduced to the micro-blogging site.
Four waves of attacks hit the site, with the worms compromising hundreds of accounts using cross-site scripting attacks.
They also had to identify and delete thousands of tweets that continued to spread the worm.
The original attack encouraged users to click on a link to a rival site called StalkDaily.com. Once they clicked, infected users automatically began to send out messages to friends, which also promoted the site.
According to security expert Graham Cluley, the later attacks were 'inspired' by the author of the original attack, using another cross-site scripting worm.
Stone said that no passwords, phone numbers or other sensitive information was compromised as part of the attacks.
Stone said Twitter was reviewing what happened, cleaning up the mess, and remained on alert.
He said: "Every time we battle an attack, we evaluate our web coding practices to learn how we can do better to prevent them in the future.
"We will conduct a full review of the weekend activities."
A 17-year-old school student called Michael Mooney acknowledged releasing the initial worm to Associated Press, which was set to promote his site StalkDaily.com. He claimed he also wanted to expose Twitter's weaknesses.
Mooney said he had second thoughts about what he had done after Biz Stone said on his blog that Twitter could pursue legal action against the culprit.
In an interview with BBC News, Mikko Hypponen, chief research officer at F-Secure, said the attack could have been much worse, as all the worm did was infect Twitter rather than computers.
He said: "It would have been simple to integrate a web browser exploit into this so that you could have done anything you wanted to the infected computer.
"[This includes] recording all keyboard strokes and capturing capturing credit card details."
This is just the latest worm attack of 2009, and it isn't the first time Twitter has had a security scare from a teenage hacker.
