Today, we are officially introducing a proof-of-work (PoW) defense for onion services designed to prioritize verified network traffic as a deterrent against denial of service (DoS) attacks with the release of Tor 0.4.8.
This is a new PoW protocol that will be used to defend against DDOSs
It’s an interesting feature and will be eager to see it in action. Surely hope it stays dormant most of the time though.