Quickly disable ssh version 1 in Linux
This is going to be very short post 
SSH v1 is not very safe and if you are looking to pass your site/server for PCI compliance then you must disable it. Don’t worry it is too easy to do.
Open /etc/ssh/sshd_config file and disable version 1:
$ vi /etc/ssh/sshd_config
find line: #Protocol 2,1 and remove 1 from it and then un-comment it, the final line should look like this:
$ cat /etc/ssh/sshd_config | grep Protocol Protocol 2
Restart SSH service to apply changes.
$ service sshd restart