Block withholding attacks, whereby a miner in a pool withholds valid blocks, have been observed recently as noted by F2Pool founder Mao Shixing. Bitcoin Core developer, Luke Dash Jr (@LukeDashjr), proposed a fix but it would require a hard fork of the Bitcoin Core protocol. In the latest Proof of Work newsletter, adoption of a more decentralized mining protocol such as Matt Corallo’s (@TheBlueMatt) BetterHash protocol at the pool level was noted as a viable solution to these attacks.
Source: Proof of Work
