Account lockout policies are specifically designed to prevent brute force attacks by locking an account after a certain number of failed login attempts. This directly mitigates the risk by stopping the attacker from continuously trying different password combinations. Using longer passwords increases the difficulty of success for an attacker but does not block continuous attempts. Frequent password changes can be counterproductive as they might lead to weaker password choices by users. Monitoring for failed logins is a reactive measure which helps in identifying that a brute force attack may be occurring but does not prevent it.