>How do we know that the Cisco equipment also isn't backdoored and if I send a few malformed TCP packets it opens up its control plane on the receiving port? N

>How do we know that the Cisco equipment also isn't backdoored and if I send a few malformed TCP packets it opens up its control plane on the receiving port? Nothing so sophisticated is required. Look at the sheer number of "default credential" and "static credential" for a whole variety of products: https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=Cisco+credential+ https://cve.mitre.org/cgi-bin/cvekey.cgi?keyword=Cisco+crede...