How Does the Difficulty Adjustment Algorithm Relate to the Security Expenditure?

The difficulty adjustment algorithm is a mechanism that automatically changes the complexity of the PoW puzzle to maintain a consistent block time despite fluctuations in total hashing power. When more miners join, the difficulty increases, requiring more computational power and thus more energy (security expenditure) to find a block.

This ensures that the cost to attack the network remains high and proportional to the network's value.