Bitcoin mining has become a very competitive market where a handful of companies are validating the vast majority of transactions. We show how the current centralization of mining power is a threat to the protocol’s security, how mining pools share block rewards and how these entities are related to each other. We further develop on who are the pools members and what’s their behavior. All our data and extracted information on mining activity (blocks, addresses and pools) will be publicly available to foster research on the field and identify possible threats.