A whirring sound in the computer room, led the rest of the teachers suspect of some illegal operation happening in the computer room.

The Principal had set up a cryptocurrency mining operation in the computer room.  This was maintained a secret until the teachers unfolded the reality. 

The BBC reported the incident.  Lei Hua works as a headmaster at the Puman Middle School in ChenZhou.  ChenZhou is a Hunan Province.  He was found to be mining Ethereum at the school premises using the electricity and computer of the school.  He was sacked after the incident was learned.

Mr. Hua was the cause of the 14,700 Yuan electricity bill, which roughly amounts to $A2940.  This bill led to all the suspicion about something happening wrong around the premises.  This bill summed up due to the machines running day and night mining cryptocurrency.

In order to make some extra money on the side, Mr. Hua started mining cryptocurrency at home. However, he realized that the system was eating up nearly 21 Kilowatt hours of electricity per day. Therefore, he shifted his computer to the school.  He further added 7 miners to the operation.  This led to an outburst of electricity bill.

Wang Zhipeng, the deputy principal of the school as well purchased the ninth machine and he too ran the machine at school. This amounted to 10 computers mining Ethereum day and night and the electricity bills soar high.

Ultimately, Mr. Hua was sacked in the past month.  Mr. Zhipeng was permitted to continue in the job after he was given an official warning about his activities.

When Mr. Hua was warned about the critical electricity bills at the school, he stated to the management that it was caused due to the cooling and heating devices that are used in the classroom.

The teachers were about to identify the constant whirring sound from the computer room, and this lead to the discovery of the machines installed in the computer room.  They have had this installed anywhere from summer 2017 through summer 2018.

This mining scheme slowed down the internet in the computer labs and children were not able to access their computers and the teachers were not able to complete their task either.

The job of cryptocurrency miners is to solve mathematical puzzles.  These are the puzzles that actually power the cryptocurrency network.  On solving the mathematical puzzle they are awarded cryptocurrency, which can in turn be converted to fiat currencies. This process consumes a great deal of electricity. This is the factor that had them caught in the process.  It is not clear about how many cryptocurrencies they managed to mint; however, in the end, they have lost their jobs.  Though the profits are known, the Chinese disciplinary commission seized the information.