Twitter has become the latest victim of cyber-attacks with "extremely sophisticated" hackers and have reportedly stolen user names and passwords for about 250,000 users.
Twitter information security director Bob Lord said: "We discovered one live attack and were able to shut it down in process moments later."
"However, our investigation has thus far indicated that the attackers may have had access to limited user information — usernames, email addresses, session tokens and encrypted/salted versions of passwords — for approximately 250,000 users," Lord said.
"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."
The company said it has reset the passwords of the affected accounts and will notify them soon.
Apart from Twitter, the Washington Post has revealed that it was also the target of a sophisticated cyber-attack, which was discovered in 2011.
Last week, the New York Times (NYT) and Wall Street Journal (WSJ) alleged that Chinese hackers have attacked their computer systems.
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Twitter has 200 million active users per month and last year the company introduced numerous new features to help bring more people to its site.
Data from GlobalWebIndex shows that the number of active users on Twitter jumped 40% from Q2 2012 to Q4 2012.
