According to a report published on the Reddit website, over 51% of Dash hashrate is controlled by NiceHash. At the moment, the Dash network hashrate is 1790 TH/s, NiceHash accounts own about 1390 TH/s (70%).
User Flenst, claims that approximately 560 TH/s out of 1790 TH/s are under the control of unknown mining pool. Flenst found out that the owner of 560 TH / s computing power receives a reward for mining Dash for 3 cryptocurrency wallets:
According to Flenst, unknown miners control 53% of the Dash hashrate can attack the blockchain cryptocurrency at any time, so he advises to closely monitor the network and follow heightened precautions. He also found out that unknown miners began to increase computing power in September 2018. Up to this point, NiceHash accounted for no more than 20% of the Dash network hashrate, however, this figure has grown to 70%.
In November 2018, Dash developers announced the start of work on consensus protocol improving in order to prevent 51% attacks on the blockchain. The developers suggested to use the “longest network” rule, according to which blockchain nodes choose the longest chain, while all short chains become inactive. If several chains of the same length appear, the nodes select the chain with the most new blocks. Thanks to this concept, it is possible to reduce the likelihood of a successful 51% attack on the blockchain.