There is an ongoing spam attack on the fediverse for the last couple of days. It's more widespread than before, as attackers are targeting smaller servers to create accounts. Before, usually only mastodon.social was targeted and our team could take care of it. For server administrators out there: If you don't need open registrations, switch over to approval mode. If you do, blocking disposable e-mail providers is a massive stopgap to the problem. Mastodon also supports hCaptcha.