When you realize that the gatekeepers (your communication carriers) have not prevented foreign actors from having unwanted presence on their networks, it is incumbent on your own organization to ensure you have robust protections in place for the infrastructure you manage.
If you're looking for an excellent set of practices, this is a great baseline of behavior for your org to attain.
Enhanced Visibility and Hardening Guidance for Communications Infrastructure | CISA
-----------
A claim is as good as its veracity.
