What Is the ‘Cost to Attack’ Metric and Why Is It Crucial for PoW Security?

The 'cost to attack' is the estimated financial expense required to acquire enough hash power (either by renting or buying) to execute a successful 51% attack over a specified duration, typically one hour. It is crucial because it represents the economic security barrier protecting the network.

A low cost signals vulnerability, as it makes the potential profit from a successful attack outweigh the expense, especially for smaller market cap coins.