DOS spam flood attack against directories & makers (thousands/sec of !orderbook cmd from random nicks)

[seamo1]

• Banning per nick is easy for the attacker to evade.
• Tor hidden services / onion host identity (onion address / service key) or connection-level identifiers are harder to rotate quickly and are better targets for persistent bans (files).
• Proof-of-work (POW) in the orderbook request, or any incoming onion connection is the proper defense; for both directory nodes & makers

Seems like @roshii has worked on POW in JoinMarket already #1808 -- anyone else try it in real life against the ongoing attack?

Tor Project background on this defense feature: https://forum.torproject.org/t/proof-of-work-pow-defense-for-onion-service-is-released/
https://onionservices.torproject.org/technology/security/pow/

[seamo1]

For reference, more details on POW & DOS implementation from the NG rewrite:
#1819 (comment)
This is also needed (txtorcon 24.8.0) #1815