CentOS

Hi Guys,

Im pretty new with Centos / Linux.
I have a VPS with Centos 7. I want to work with Kerio Connect (mail server).

The first thing I did after installing Centos is change the SSH port (default 22 to other port).
After that, I have installed cryptsetup, which is needed for Kerio Connect.
After that, I installed Kerio Connect succesfully with also a valid SSL certificate from CoMoDo.

In Kerio Connect, i disabled all services like pop3, imap, nntp, xmpp, bec i use it with Active Sync and webmail.
Only running port are 80,443, 25, 587 and 465.

Now my questions.
1) Do i need to install a firewall? Why I ask: i run only the common ports for email and the edited SSH port.
2) Do i need to install an antivirus?
3) Do i need something more to secure the VPS?

Thanks for answering!

firewalld is the default firewall, and unless you have disabled/stopped it, it runs with the default rules.

You can install ClamAV from EPEL , firewalld is easy to use so you can leave it this way.
Using non-standard port requires some SELINUX changes, but it's not rocket science.

I would recommend you to keep SELINUX in 'enforcing' mode (enabled by default).