Last week, Decrypt Media published an article outlining the practice of spy mining on the Ethereum network–a practice whereby a miner eavesdrops on other mining pools to gain an unfair advantage in producing and verifying blocks. One of the main culprits–there were others–Etherdig has managed to mine more than 1,250 blocks, earning 3,750 ETH ($862,500) in mining rewards, without processing a single transaction.

This raises serious questions for Ethereum. If miners were allowed to gain an unfair advantage by eavesdropping on other blocks, transactions across the network would take longer as they have to wait for blocks mined by miners with actual transactions in them to be verified. We saw precisely that last month, where the number of empty blocks on the network rose by 637 per cent. The good news, however, is that it appears Etherdig has had a change of heart.

On October 5, at 4.04 AM (UTC), Etherdig mined its last empty block which took just three seconds. It has not mined a block since, bringing an end to its practice of spy mining on the Ethereum network, for now. The Etherdig website has a statement that says mining has been stopped and that the service is going to be reorganized.

It is unclear whether the service was stopped due to the criticisms of its spy mining practice or due to the relatively low price of Ether, which makes mining it less profitable, or potentially loss making. A moderator on the forum bits.media, where a thread discusses the mining pool, also writes that an analysis was set to be carried out on the economic feasibility of continuing the mining pool and a negative decision would result in the pool being stopped. However, Etherdig is still operating on Ethereum Classic and has 0.54% of the network’s computing power, or hashrate. While it is regularly mining empty blocks, that is standard practice on the network because there are so few transactions.

F2Pool explains its empty blocks

In our previous article, we also examined F2Pool, one of the biggest mining pools, and its practice of mining empty blocks alongside regular, transaction-filled ones. It asserted that the mining pool was performing “selfish mining”--a term referring to when a mining pool holds mined blocks back in order to publish several of them in one go to the network, giving them a time advantage against other pools.

F2Pool has clarified to Decrypt Media that empty blocks are produced as part of an ongoing process of optimizing its hashrate in order to account for network delays. F2Pool sends out the block header which can be used to make an empty block a couple of seconds before it sends out the whole block. This means, if a block is found within that time period, then an empty block is published.

“Actually, as the pool, we do not want to see empty blocks coming out. After all, the transaction fee is a big source of income. However, to prevent the miners losing out from hashrate waste, F2Pool will still send a mission (block header) to miners on time, even though that may cause empty blocks,” says Zhe Zhang, a spokesman for F2Pool.

However, the Ethereum network is still vulnerable to manipulation. In August, a hacker managed to end the notorious exit scam Dapp–where the final person to put money in a pot takes it all–called Fomo3d, by spending $11,000 to bung up the Ethereum network so other transactions couldn’t go through. Cut to today, and we can see that a few unscrupulous actors can create the same slowdown. Ethereum wants to be the platform everyone builds on but before it becomes that, it has to find a way to make everyone play fair.