One of the most insecure parts of an online PBX is the management web GUI. Restricting access to this is highly desirable and protects you from unpublished vulnerabilities.
One way is to use IPTables to limit certain IP addresses (http://sysadminman.net/blog/2011/restricting-web-interface-access-with-iptables-2156) but this relies on you having a fixed IP address.
Another, more flexible way, is to block all access via ports 80/443 (http/https) and access the system through a secure SSH tunnel using Putty.
If you have a SysAdminMan VPS and would like this setting up please get in touch.
First we need to block access to port 443/80. Do this be logging on as root and then running the iptables command to identify the rules allowing access. You may only see rules for port 80 or 443 depending on your system setup –