The DNS checking service is rate limited and adds latency, but there is a bulk exit list available here; https://check.torproject.org/torbulkexitlist (please don't use 3rd party blocklists, as those often contain middles and guards, even though traffic cannot leave those kind of relays).
But, before you block Tor, please consider that doing so will most likely block a number of legitimate users who you haven't noticed before - just to stop one jerk. Instead, you could restrict access to certain parts of your site for Tor visitors for example.
Bot traffic from Tor is usually of the easily detectable variety (as the attacker didn't have enough skill to build/acquire a botnet and get "clean" IP's),
The new blocking completely blocks access to the site, not just posting. See for yourself; https://www.torproject.org/
Tor is next to useless for DDoS attacks, as it doesn't offer any amplification. For every byte you send in via TCP, you get one byte out. For attackers with large botnets, it doesn't make sense to DDOS over Tor, as the number of exiting IP addresses are limited and it's easy to block them all. It makes more sense to use your thousands of available botnet IP's that aren't on any lists.
The DNS checking service is rate limited and adds latency, but there is a bulk exit list available here; https://check.torproject.org/torbulkexitlist (please don't use 3rd party blocklists, as those often contain middles and guards, even though traffic cannot leave those kind of relays).
But, before you block Tor, please consider that doing so will most likely block a number of legitimate users who you haven't noticed before - just to stop one jerk. Instead, you could restrict access to certain parts of your site for Tor visitors for example.
Bot traffic from Tor is usually of the easily detectable variety (as the attacker didn't have enough skill to build/acquire a botnet and get "clean" IP's),