An account created by a hacker known as Cairo has become the subject of an investigation by Twitter and Facebook.
A spokesperson for the company told Motherboard that the company had received a “threat of serious harm” from the hacker, and was investigating.
Twitter and the company did not specify which account had been hacked, but the statement said that “we are aware of the threat and are taking steps to protect our users.”
The hacker is known to be connected to another hacker group, Anonymous, and the account is one of the most popular in the hacking group’s network, the spokesperson said.
Twitter is reportedly looking into the threat.
In February, Twitter’s parent company, Alphabet, said that it was working with law enforcement agencies on the investigation.
Anonymous has previously hacked Twitter accounts, and in April it claimed to have released information on more than 40,000 accounts, including accounts belonging to the U.S. intelligence community.
In July, Twitter announced that it would be banning the use of its platform to send mass amounts of information to third parties.
In August, Facebook announced it was investigating the possible involvement of a “botnet” of accounts, one of which was found to have been created by the hacker known to the public as Caio.