John works as a professional Ethical Hacker. He has been assigned a project to test the security of www.we-are-secure.co

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John works as a professional Ethical Hacker. He has been assigned a project to test the security of www.we-are-secure.com. He successfully performs a brute force attack on the We-are-secure server. Now, he suggests some countermeasures to avoid such brute force attacks on the We-are-secure server.
Which of the following are countermeasures against a brute force attack?

A. The site should use CAPTCHA after a specific number of failed login attempts.
B. The site should increase the encryption key length of the password.
C. The site should restrict the number of login attempts to only three times.
D. The site should force its users to change their passwords from time to time.