What does this IPTable rule (SV-50313r2_rule) mean?

Question

The operating system must prevent public IPv4 access into an organizations internal networks, except as appropriately mediated by managed interfaces employing boundary protection devices.

What does this statement trying to say?

…must prevent public IPv4 access into an organizations internal networks…

Isn’t an organization’s internal network is already (hopefully) private?

…managed interfaces…

What are they?

Answer 1

You seem to be quoting the IPTables “50313r2_rule” rule.

It’s basically a simple concept once you get by the attempts at jargon and complexity. Here is my breakdown:

The operating system must prevent public IPv4 access into an organizations internal networks…

On a default level—outside of additional software concerns—the base operating system should not (by default) grant wider access to the LAN the system is connected to. This is mostly commonsense/default behavior. And this kind of default behavior can often be circumvented by installing additional software on a machine—such as a server—or enabling a service in the OS.

…except as appropriately mediated by managed interfaces employing boundary protection devices.

A “managed interface” is just any network interface that is managed. So “management” can often refer to simply enabling or tweaking firewall software or built-in firewall rules in the OS. The phrasing of “boundary protection devices” is really confusing because such a “device” can simply be firewall software configured to pay attention to a specific physical port on a machine.