There have been a tremendous amount of Bitcoin cloud mining scams. Genesis Mining is the largest Bitcoin and scrypt cloud mining provider.
Genesis Mining offers three Bitcoin cloud mining plans that are reasonably priced. Zcash mining contracts are also available. Hashing24 has been involved with Bitcoin mining since They have facilities in Iceland and Georgia.
Minex is an innovative aggregator of blockchain projects presented in an economic simulation game format. Users purchase Cloudpacks which can then be used to build an index from pre-picked sets of cloud mining farms, lotteries, casinos, real-world markets and much more. Offers both pool and merged mining and cloud mining services for Bitcoin.
Hashnest is operated by Bitmain, the producer of the Antminer line of Bitcoin miners. This number is called the mining difficulty. The mining difficulty expresses how much harder the current block is to generate compared to the first block. So a difficulty of means to generate the current block you have to do times more work than Satoshi Nakamoto had to do generating the first block. To be fair, back then mining hardware and algorithms were a lot slower and less optimized.
To keep blocks coming roughly every 10 minutes, the difficulty is adjusted using a shared formula every blocks. The network tries to change it such that blocks at the current global network processing power take about 14 days. That’s why, when the network power rises, the difficulty rises as well. In the quest to further secure the network and earn more bitcoins, miners innovated on many fronts and for years now, CPU mining has been relatively futile.