Twitter sent notices of an attempted hacking to China-based foreign journalists and analysts just hours before apologizing for resetting the passwords of more users than necessary in a recent break-in of accounts.The Voice of America reported Thursday that the emailed warnings did not say who was behind the hacking attempts. Chinese Internet users have had difficulty in accessing foreign websites and using virtual private networks (VPN) to avoid government censorship, the U.S.-funded VOA said.Twitter routinely sends warnings when it believes a person's account has been hacked. The microblogging site then forces the person to reset his password. On Thursday, the company apologized for resetting more passwords than necessary to protect users from a recent hacking."In this case, we unintentionally reset passwords of a larger number of accounts, beyond those that we believed to have been compromised," Twitter said in a tweet. "We apologize for any inconvenience or confusion this may have caused."Twitter, which did not respond to a request for comment, has provided no details on the hacking. However, VOA reported that journalists and analysts have been expecting a censorship crackdown as China's Communist Party begins meetings to set in motion a leadership change.David Bandurski, head of the China Media Project in Hong Kong, told VOA he received a warning that his Twitter account had been hacked just as he was tweeting\u00a0 about Chinese President Hu Jintao's speech at the 18th Party Congress."I had someone else, a programmer, look at it and say that's a legit message from Twitter,"\u00a0Bandurski told VOA. "Beyond that I don't know what that means or who could be behind it. I have my guesses that I won't hazard, but I'm not sure what to say other than that it's an annoyance."[See also:\u00a0Chinese official defends Internet censorship]Contacted by email, Bandurski declined to provide more details. "I've been very careful to explain to reporters that I'm not speculating about what happened, that they need to find out from Twitter," he said.Prolexic, a security vendor specializing in distributed denial of service (DDoS) attacks, said it had not seen any significant changes in activity out of China. "It has maintained its position as one of the top three countries originating DDoS traffic over the last 2 quarters," a spokesman said.Hackers with stolen user names and passwords will hijack Twitter accounts to distribute links that send users to malicious websites. Cybercriminals are also opening accounts to tweet commands to malware controlling compromised PCs, McAfee reported recently in its second quarter Threats Report.\u00a0Overall, four in 10 social network users have been victims of cybercrime on the platforms, according Symantec's 2012 Norton Cybercrime Report. In addition, one in six reported that someone had hacked into their profile and pretended to be them.A U.S. commission has fingered China as the biggest cyberthreat, due to relentless attacks against U.S. military systems and defense contractors. The U.S.-China Economic and Security Review Commission is scheduled to release its findings to Congress next month.