Securing SSH Access
(posted 2018.12.01, last updated 2022.09.21)

[Tested for Ubuntu 18.04]

First I would like to secure my server against Bruteforce attacks, at least for ssh.

Prevent password authentication:

If it does not exist, create a '.ssh' directory and give it the proper permissions.

mkdir ~/.ssh
chmod 0700 ~/.ssh
touch ~/.ssh/authorized_keys
chmod 0600 ~/.ssh/authorized_keys

Add your key to the list of authorized keys echo "ssh-rsa AAAA[...]mmMveIJc= SomeCommentForTheKey" >> ~/.ssh/authorized_keys
Activate key based authentication nano /etc/ssh/sshd_config

Find and update the following setting to the given value.
```
RSAAuthentication yes
PubkeyAuthentication yes
```

Try to login using your Private Key. (!!! Try before disabling Password based login !!!)
Disable Password-based authentication. nano /etc/ssh/sshd_config

Find and update the following setting to the given value.

ChallengeResponseAuthentication no
PasswordAuthentication no
UsePAM no

Change SSH Port to something not default (22):

Edit sshd config. nano /etc/ssh/sshd_config
Update the following variable: Port 11111 # or any other port not used by your server