I'm a starting a small service practically. And I have single server currently. No money to purchase separated/dedicated firewall equipment now.
Is it effective installing firewall software on same machine which offering internet service? My server will offer HTTP, NFS, and SSH, and custom made server software on a several ports.
All services (except NFS) should be open to internet. Not internal services. I guess my machine (virtualized within
Xen) is connected to the internet directly because I can connect to my machine SSH with only IP address.
(edit) NFS is not open to internet. Sorry for my mistake. NFS will be served via SSH only.