Twitter said the hack took place after a third-party group executed "a coordinated social engineering attack" against its employees to gain access to its backend and used internal tools to send out tweets on behalf of verified high-user-count profiles.
Defaced accounts included profiles for former US President Barrack Obama, former US Vice-President Joe Biden, celebrities like Kanye West and Kim Kardashian, but also tech companies like Apple and Uber. In total, Twitter said that hackers targeted around 130 accounts, but managed to tweet only on the behalf of a few of those.
Twitter stopped the attack yesterday by blocking verified accounts from sending out new tweets before rooting out the hackers from its backend.
Verified accounts were locked for a few hours before being reinstated.
Today, Twitter also blocked all of its users from tweeting strings that featured formatting similar to a Bitcoin address, making the job of some security analysts and code developers harder, as the measure also blocked some of their workflows that featured similar-looking strings (such as file hashes and Git file paths).