Twitter is warning some users that governments might be trying to hack their accounts. The microblogging service sent emails to an unknown number of users warning that hackers may be trying to obtain phone numbers, email addresses and IP addresses, according to Twitter users who have received the emails. The emails go on to advise users to take proper precautions to safeguard their personal information, including offering a link to information on Tor, software that allows for anonymous communication on the Internet. The warning, like similar ones issued previously by Facebook and Google , underscore the growing frequency of state-sponsored hacks, typically used to steal government information or intellectual property.