Test if a socket accept is from external network

[Jeffrey Walton]

On Sun, Apr 25, 2021 at 7:09 AM John Wood <john.wood at gmx.com> wrote:
>
> I'm working in a LSM to detect and mitigate fork brute force attacks
> against vulnerable userspace applications. Now, to fine tuning the
> detection I want to detect a network activity.  ...
> How can I detect that an external connection (using a net device) is
> accepted and avoid internal network communication?

One caveat that may (or may not) apply...

Systemd opens sockets for services even when a service is disabled. It
could appear that a system is accepting traffic even when the service
is unavailable.

Jeff