Certainly Brujo.
In sshd_config, I removed the line: Subsystem sftp /usr/libexec/openssh/sftp-server
and replaced it with: Subsystem sftp internal-sftp
Then I added the following rules to sshd_config, one for each user:
Match User username
ChrootDirectory /var/www/vhosts...
Why on earth would I ever want to implement port knocking to simply to pass a PCI test designed for my protection when all I have to do is implement a security update which is unavailable to plesk because the maintainers only support an outdated library?
I might add that the failure is not a result of penetration testing. The failure is generated by a simple check of the OpenSSH version number. Otherwise, the server passes all other PCI checks.
Thanks, but no, that does not apply. My issues is described in CVE-2017-15906. IP blocking will not work for me because we have drivers on the road accessing over public networks.