Re:Ask HN: Anonymous person sent proof of SSH access to our ...
by TheDong on Wednesday July 27, 2016 @11:54PM
(#12178219)
removing firewalls has effectively no benefit; a non-root user can trivially download and run an arbitrary distro or package manager (e.g. nix from nixos, portage from a gentoo prefix, etc) and effectively do a chroot + package management without root.
However, proper ingress filtering or local iptables/pf rules would stop any unwanted inbound traffic from reaching your server, and you should definitely be using ingress and egress filtering on your network.