Dictionary attacks involve an attacker attempting to guess passwords by using a list of common passwords.
Implementing a lockout policy is effective because it limits the number of login attempts, thereby hindering the attacker's ability to repeatedly attempt different passwords. Lockout policies are standard in cybersecurity practices to prevent brute-force and dictionary attacks by temporarily disabling an account after a certain number of failed login attempts. According to CompTIA Security+ standards, password complexity (option B) and multifactor authentication (option A) are helpful but are not as immediately effective in directly preventing repeated attempts as a lockout policy.