BlockFi temporarily closed new registrations due to an attack by a malicious actor as its 500 users received profanity-laced correspondence from BlockFi. A single attacker had begun the registration process for more than 1,000 fake accounts, using email addresses belonging to real users. The attacker then entered “vulgar and racist” terms as the first and last names for the fake accounts, resulting in about 500 emails with the offensive language being sent out automatically before BlockFi halted registrations.