Spyware Mining (Spy mining) - this is not a completely honest method of accelerating the production of cryptocurrency, as a result of which miners write empty blocks without transactions into the blockchain. This method increases the profitability of pools, but is of no benefit to the network, because user transfers are not processed.
Spy mining works as follows. Mining pools watch each other with the help of their spies and track the hash rates of blocks mined by competitors. They use this information to quickly find the next block, deliberately not including transactions in it in order to be the first. Such an empty block contains only one base Coinbase-transaction, which is a mining reward.
In anticipation of the approaching hardfork Ethereum Constantinople, such pools as F2Pool and Etherdig began to intensively engage in espionage mining. Etherdig alone extracted 1250 empty blocks, earning an 3750 ETH. The fact is that after updating etherium, the reward for PoW mining will be significantly reduced. Therefore, pools want to break the bank, while there is such an opportunity.