How Can a Blockchain Network Defend against a 51% Attack?

A blockchain network can defend against a 51% attack through several mechanisms. One is to increase the network's hash rate, making it more expensive for an attacker to gain control.

Another is to implement a "modified proof-of-work" algorithm that is resistant to specialized mining hardware. Some networks may also have built-in checkpoints or emergency protocols that can be activated in the event of an attack.

Finally, the community can coordinate a hard fork to a new chain, effectively invalidating the attacker's chain.