Protecting Your Server with SSH Client 4.60 and Multiple Authentication Methods

When it comes to securing your server, one of the most effective ways to do so is by setting up multiple authentication methods for SSH access. This can be achieved using the `AuthenticationMethods` option in the SSH daemon configuration file. With this option, you can specify which authentication methods are required for connecting to your server.

One of the benefits of using multiple authentication methods is that it makes it more difficult for malicious users to gain unauthorized access to your server. For example, you can set up two-factor authentication and public key authentication, making it virtually impossible for an attacker to compromise your server.

Before adding this configuration option to your SSH daemon, make sure that all accounts that require SSH access have public-key authentication set up in the corresponding authorized_keys files. This is crucial to prevent any potential security risks.

To disable password logins entirely and force the use of SSH keys, you can add the following options to your daemon configuration file:

`/etc/ssh/sshd_config.d/20-force_publickey_nf`

`PasswordAuthentication no`

This will ensure that any client attempting to connect to your server using a password will be denied access. Instead, the client will need to use an SSH key for authentication.

Another effective way to protect against brute force attacks is to limit remote log-on through SSH. This can be achieved by setting up rate limiting or IP blocking. You can also consider disabling password logins entirely and forcing the use of SSH keys.

To monitor connection attempts in the log, you can run `journalctl -u sshd` as root or `journalctl /usr/bin/sshd` as root. However, if you are using socket activation, you will need to check the logs of each transient instance separately.

When exposing your server to the WAN, it is recommended to change the default port from 22 to a random higher one like this:

`Port 'random_port'`

To have sshd use a particular key, specify the following option:

`HostKeyAlgorithms rsa, ecdsa, ed25519`

Three key pairs are provided based on these algorithms. Public and private host keys are automatically generated in `/etc/ssh` by the `sshdgenkeys` service and regenerated if missing.

To configure the banner displayed when a user connects to your server, add the following option:

`Banner /etc/issue`

To allow access only for some users, add this line:

`AllowUsers 'usernames'`

Whenever changing the configuration, use `sshd` in test mode before restarting the service to ensure it will be able to start cleanly.

In conclusion, setting up SSH client 4.60 with multiple authentication methods is an effective way to protect your server from unauthorized access. By disabling password logins and forcing the use of SSH keys, you can significantly reduce the risk of brute force attacks. Additionally, monitoring connection attempts in the log and limiting remote log-on through SSH will help prevent malicious users from gaining access to your server.

References:

* Ssh-audit: An automated analysis of server and client configuration.

* `journalctl`: A command-line tool for monitoring system logs.

* `sshdgenkeys`: A service that generates public and private host keys.

Serial number bitvise ssh client 4.60