Tor Project statement on today's attack.
This looks like a regular attempt at a Sybil attack: the attackers have signed up
many new relays in hopes of becoming a large fraction of the network.
But even though they are running thousands of new relays, their relays
currently make up less than 1% of the Tor network by capacity. We are
working now to remove these relays from the network before they become
a threat, and we don't expect any anonymity or performance effects based
on what we've seen so far.