What Defensive Mechanisms Can Smaller Cryptocurrencies Implement to Protect against Attacks from Rented Hashrate?

Smaller coins can implement several defensive mechanisms. One key strategy is to use an ASIC-resistant mining algorithm, which prevents the use of highly specialized and powerful mining hardware that dominates hashrate rental markets.

Another defense is to implement a checkpointing system, where developers periodically hardcode a 'correct' version of the blockchain history, making it impossible to rewrite. Some coins adopt hybrid Proof-of-Work/Proof-of-Stake consensus models to increase the cost and complexity of an attack.

Finally, actively monitoring hashrate rental markets for large purchases targeting their algorithm can provide an early warning.