Twitter warned over the weekend that it had detected a live attack on its systems, in which unknown miscreants attempted to gain unauthorised access to data on the social network.
While Twitter was able to shut down the attack soon after it was noticed, the company's director of information security, Bob Lord, said that data for approximately 250,000 users may have been accessed.
The information targeted included user names, email addresses, session tokens used to keep track of what logged in users do on Twitter, and encrypted passwords with random data used to "salt" them, for improved security.
Twitter has reset the passwords and revoked session tokens for the accounts affected by the attack Users whose accounts may have been compromised will have to create a new password when the log in next to Twitter.
Among the more prominent victims of the attack were Om Malik, of large tech business blog Giga Om who tweeted:
damn that was fun. that is resetting my password after being compromised. But I appreciate @twitter being proactive about it— Om Malik (@om) February 2, 2013
Lord said only a small number of Twitter users were affected by the attack, but the social network nevertheless encourages people to use strong passwords, at least ten characters long and a mix of alphanumeric symbols.
Although Lord provides no further detail as to how the attack took place, he said Twitter encourages users to disable Java on their computers.
Oracle's Java has been favoured by attackers for a while now, with zero-day exploits being sold as part of crimeware packs. At this stage, it is not known if a Java exploit was behind the recent Twitter attack.
"This attack was not the work of amateurs, and we do not believe it was an isolated incident.
"The attackers were extremely sophisticated, and we believe other companies and organizations have also been recently similarly attacked.
"For that reason we felt that it was important to publicise this attack while we still gather information, and we are helping government and federal law enforcement in their effort to find and prosecute these attackers to make the Internet safer for all users," Lord says.
iTnews has asked Lord for further details on the attack and will update the article when they're available.