The protocol zero is what is reported by the wallet's getpeerinfo to the explorer.

I'm not 100% sure what it is, though it pops up occasionally on various wallets wallets.

My best guess so far is not that it is a sign of a hack, but either a connection problem by a peer, or a cloned wallet where the "magic bytes" were not changed to something unique, so the cloned wallets passes initial connection check which allows it to get listed in the peer list, then fails all the further checks.

Difficulty rise was caused by one of the largest stakeholders staking.