Researchers identify an attack strategy actively being used by the second-largest Ethereum mining pool to earn outsized mining rewards

Researchers from The Hebrew University have identified an attack on the consensus mechanism used by Ethereum which they describe as risk-free and which can used to "obtain consistently higher mining rewards compared to the honest protocol". They also identified that the attack was being actively used by F2Pool's Ethereum mining pool to attack other mining operations. F2Pool is the second-largest Ethereum mining pool.

By manipulating the timestamps of blocks to be added to the chain, a miner can replace other miners' main-chain blocks with their own blocks, obtaining the fees that would have gone to the other miners. The attack has been called an "Uncle Maker" attack because Ethereum refers to valid but not main-chain blocks as "uncles".

F2Pool co-founder Chun Wang responded on August 8 to the allegations against his mining pool, apparently acknowledging their behavior and suggesting that manipulating a vulnerability in a system is not a "blatant disregard [of] the rules" as the researchers had characterized it. He tweeted: "We respect the *consensus* as is. If you don't like the consensus, convince [Ethereum developer Tim Beiko] to send me another Announcement and change it." Quote-tweeting a tweet by the lead author of the paper who described F2Pool's technique, he wrote, "I can't stop appreciate this elegant implementation of what we've done over the past two years... A robust system must withstand all kind of tests."