A Chinese headmaster was fired after finding a secret pile of crypto coin mining machines related to the electricity supply of his school.
Teachers at the Hunan school became suspicious of a humming sound that continued to last day and night, local media reported.
This led to the discovery of the machines that exploited the crypto-currency Ethereum.
They paid an electricity bill of 14,700 yuan (£ 1,600).
Excessive electricity consumption was previously reported to the director, Lei Hua, but he reportedly dismissed it as caused by air conditioners and heaters.
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Mining crypto coins such as Bitcoin and Ethereum include connecting computers, mostly specialized "mining machines," with the currency network.
By providing computing power for validating transactions on that network, owners of mining machines are rewarded with newly generated coins, making it a potentially lucrative exercise – especially if it is done on a large scale.
In this case, in the summer of 2017 and in the summer of 2018, a total of eight mining machines were installed in the computer room of the Hunan school.
The principal had originally spent 10,000 yuan on a single machine for home use, but reportedly moved to the school after seeing how much electricity it had consumed.
The deputy chief executive also became involved in the scheme and allegedly purchased a ninth machine for himself in January, which was also installed at the school.
The computer network in the building became overloaded due to mining activity, according to reports, and this & # 39; interfered & # 39; with education.
The headmaster was dismissed in October and his deputy received an official warning.
A local authority responsible for "discipline inspection" has claimed the money that was made by the mining activities.
"The noise and heat of nine active mining machines would have been very noticeable," said Matthew Hickey, a cybersecurity expert at Hacker House.
"Unfortunately, stealing electricity is a way people have tried to maximize their revenues – by avoiding those costs it can drastically improve the output of a mining industry."
Surreptitious crypto-currency mining has been discovered elsewhere. In February, several scientists from an extremely secret Russian nuclear warhead facility were arrested because they would have mined Bitcoin with the supercomputers of the facility.