It is a well-known fact, that every blockchain-based cryptocurrency is prone to the 51% majority attack. In short, a miner or a group of miners controlling more than a half of the network's hashrate can try to manipulate transaction chain and validate it at the same time. Posessing the most hashing power on the network gives a chance that such chain will survive as the longest on the network and therefore be accepted by the network's consensus.

To make sure blockchain can serve it's role as a trusted and decentralized platform, the honest miners must consist of at least 50% of the hashing power in the system.

In the history of Bitcoin, there were a few moments where such situation raised community's concern. Affected mining pool assured to voluntarily hold down a part of it's hashrate in case of exceeding 50% network share.

Moreover, thanks to the probabilistic nature of Bitcoin's algorithm, 51% is only a theoretical value. One could say, it is still technically possible with as much as 45%.

Let's see how it looks in case of Bitcoin (BTC) as of this writing:



It is not an overstatement to say, BTC's hashrate is well distributed among the participants (miners).

But now is the all-new contender, Bitcoin Cash (BCH) at play:



The difference is obvious and questions arise instantly.

Bearing in mind that most of the well-known mining companys/pools are not supporting forked chain yet, what party stands behind blocks mined as "unknown"? Is it one actor or is there many of them?

If it is a group of actors, do they collaborate? How can one be sure the network isn't already compromised?

Because of vastly reduced difficulty on the BCH chain (currently down by 87% comparing to BTC), it is remarkably easy task to perform a majority attack. Thanks to well-developed mining infrastructure, there is enough hashing power in the world ready to launch against the pretending blockchain. Given the fact that now over 90% of the hashrate on the forked chain comes from an unknown source, it is safe to assume that: