To keep your device secure offering as little of an attack surface as possible is a basic recommended strategy. You achieve this by not installing any unnecessary software that might allow a break-in happen due to a conceptual error.
Furthermore it is advisable to only open those TCP/UDP ports that are absolutely necessary for communication with other hosts in the LAN and the Internet. You can do this with the iptables contained in the Linux kernel and the “Uncomplicated Firewall” as a configuration tool.
Our Armbian-based Cardano-on-the-Rocks image automatically installs the UFW firewall and initially only allows SSH connections for system management. Additional ports, e.g. for the Cardano-node, have to be activated as necessary.
Learn more about this at https://help.ubuntu.com/community/UFW
Our Node-related lessons will contain explanations about the additional ports and settings as required.
Security hardening for Cardano stake pools is not merely about simply following a guide once and you are done with it. Security hardening is one of the pool operators main tasks in order to achieve a solid uptime. One classic SysOps security strategy is to not tell everyone all the measurements and techniques, so there will always be more that you can figure out yourself to do better.
There are many security hardening guides out on the Web. For example you may wish to check out: