**Tor v0.4.8.1-alpha: Onion Service Proof-of-Work**
When onion service proof-of-work is widely implemented amongst nodes, the Denial of Service (DoS or DDoS) attacks that have plagued the network for years could be considerably lessened. For now, the feature is disabled by default.
https://www.nobsbitcoin.com/tor-v0-4-8-1-alpha/