Change ssh protocol in CentOS 7

SSH has two protocols that can be used, protocol 1 and protocol 2. More about SSH you can found on Wikipedia.

The older protocol 1 is less secure and if you don't specifically need you should disabled it.

To do thatopen ssh config file:

$ vi /etc/ssh/sshd_config

Change to use only protocol 2

# Protocol 2,1
Protocol 2

Save and exit the file.

Restart the ssh service:

$ systemctl restart sshd.service

If you didn't changed the default ssh port yet, you probably want to do that too.