Twitter has notified some users that their accounts may have been hacked by state-sponsored actors, as the company works to investigate the attack. "We believe that these actors (possibly associated with a government) may have been trying to obtain information such as e-mail addresses, IP addresses, and/or phone numbers," Twitter wrote in an e-mail sent on Friday.

Twitter didn’t say in the message what countries may have been behind the latest attempts to access the accounts, some of which were owned by users involved in security and free speech.

The e-mail from Twitter included links to the Tor Project and an Electronic Frontier Foundation website on safety when using social networks. Runa Sandvik, a privacy researcher, said that the e-mail didn’t offer users much information to effectively protect themselves.

"It doesn’t say what I should do next -- should I change my password? My e-mail address?" Sandvik said. "I’m hoping that Twitter is spending the resources that it needs to actually look into this and figure out what happens."