The system passed the fork today around 14:30 UTC at block 2463000 as a part of a bigger plan to defend Ethereum from the recent two-week long “sustained attack”.
In a detailed report on the corporate blog one of the chief Ethereum devs Martin Swende explained:
“A hard-fork based on EIP 150 version 1c will be put into effect at block . This will reprice certain operations to correspond better to the underlying computational complexity. A second hard-fork will follow shortly after. This fork will serve to remove accounts which are empty; lacking code, balance, storage and nonce == 0.”
Initially, the creators of Ethereum planned to implement the fork at the block 2457000 but later decided to postpone it to have more time for testing.
The team warned the community in advance to get prepared. “Hardfork in 24 Hours know, upgrade your clients,” read the top message in the r/Ethereum subreddit.
The team has used hard forks before to defend the system against hacker attacks. In July, after TheDAO crisis, Ethereum developers decided to roll back the blockchain to prevent the leak of funds from the compromised network. However, although the major part of the community switched to the new blockchain (ETH), not everyone was happy about it and a parallel project Ethereum Classic (ETC) emerged. Supporters of ETC claim to preserve the original censorship-free platform.