Which of the following lines in the sshd configuration file should, if present, be changed...

The sshd configuration file is used to customize the behavior of the SSH server daemon. Some of the lines in the file can affect the security of the server and should be modified accordingly. The following are two examples of such lines:

Protocol 2, 1: This line specifies the SSH protocol versions that are supported by the server. The possible values are 1 and 2, where 1 is the older and less secure version and 2 is the newer and more secure version. The recommended value is 2, as it provides stronger encryption, authentication, and integrity mechanisms. Allowing protocol 1 can expose the server to various attacks, such as man-in-the-middle, replay, and insertion attacks. Therefore, this line should be changed to Protocol 2 or commented out (as protocol 2 is the default value).

PermitRootLogin yes: This line determines whether root login is allowed on the server. The possible values are yes, no, prohibit-password, and without-password. The value yes allows root login with any authentication method, including password. This can pose a serious security risk, as root is the most privileged user on the system and can perform any action. If an attacker manages to guess or obtain the root password, they can gain full control over the server. Therefore, this line should be changed to no or prohibit-password (which allows root login only with public key authentication) or commented out (as no is the default value).

References: LPIC-2 202 exam objectives, LPIC-2 202-450 Exam Prep: Network Configuration, The Best Ways to Secure Your SSH Server, Configure the /etc/ssh/sshd_config file

Linux SSH Server (sshd) Configuration and Security Options With ...1

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