What Is the Risk of a 51% Attack and How Does It Relate to Large Mining Pools?

A 51% attack occurs when a single entity or group controls more than 50% of the network's total hashing power. This control allows them to potentially disrupt transaction confirmation, reverse their own transactions (double-spending), and prevent other miners from completing blocks.

Large mining pools concentrate hashing power, making them a potential vector for a 51% attack if the pool operator or a small number of members collude.