Last November the Bitcoin Cash (BCH) community witnessed a hash war that resulted in a bifurcation of the main chain. The spat saw one of the first examples of the alpha miner strategy and an attempt to truly test Nakamoto consensus. About a week before the fork, a new mining operation was announced called Shark Pool aimed at explicitly attacking weaker chains. However, a new type of mining organization revealed itself on Feb. 15 called Orca Pool which seeks to protect altcoins and forks from being attacked by malicious miners.
https://news.bitcoin.com/orca-pool-mining-operation-aims-to-defend-altcoins-and-forks-from-attacks/