Bitcoin's Anti-Censorship Ethos Surfaces After Mining Pool F2Pool Acknowledges 'Filter'

F2Pool, the third-biggest Bitcoin mining pool, drew ire on social media after a report that it might be censoring transactions from an address subject to U.S. government sanctions.

One of the F2Pool project's leaders subsequently appeared to confirm the report, stirring up controversy since "censorship resistance" is considered by many Bitcoiners to be a cardinal principle of the largest and original blockchain. At the same time, many government officials around the world have expressed concern that blockchain networks can be used to finance criminal activity and terrorism.

The Bitcoin development-focused blogger 0xB10C wrote Nov. 20 that his "miningpool-observer" project "detected six missing transactions spending from OFAC-sanctioned addresses." OFAC stands for the Office of Foreign Assets Control, a lead agency in U.S. government efforts to enforce economic sanctions.

A few of the instances "are likely false-positives and not the result of filtering," the blogger wrote.

"The transactions missing from F2Pool's blocks are, however, likely filtered," according to the piece, which was cross-posted to the website Stacker News.

A Bitcoin mining pool is where operators working to confirm transactions on the network join together to coordinate their efforts and then share any resulting rewards – typically with the goal of providing a steadier income stream.

Because they end up controlling big chunks of the network's processing, or "hashpower," their decisions can have broad ramifications. And participants in a mining pool can, relatively easily, switch to a different pool.

F2Pool is responsible for about 14% of mined Bitcoin blocks over the past year, the third-most after Foundry USA's 30% and AntPool's 22%, based on data from Blockchain.com.

F2Pool co-founder Chun Wang subsequently posted on X (formerly Twitter), "Why do you feel surprised when I refuse to confirm transactions for those criminals, dictators and terrorists? I have every right not to confirm any transactions from Vladimir Putin and Xi Jinping, don’t I?" The post has since been deleted.

Chun later wrote that "a censorship-resistant system must be designed to resist censorship at the protocol level, rather than relying on each participant to act conscientiously and refrain from censorship."

"The Internet and TCP/IP have failed this," he added. "Bitcoin should learn from the failure."

A couple hours after that, Chun tweeted again, "Will disable the tx filtering patch for now, until the community reaches a more comprehensive consensus on this topic." The term "tx" is often used as shorthand for "transaction."

Based on the replies on X, the community reaction was quite negative.

"The community has been in consensus on this for a very long time. You don't do it," one poster wrote.

"Expect blowback," a poster wrote.

Another jab displayed the project's name prominently next to the U.S. Treasury Department's seal: