https://blogs.damiendye.uk/en/tags/sip/ Recent content in Sip on Damien Dye's Blog Hugo en-GB Mon, 14 Sep 2026 09:00:00 +0100 https://blogs.damiendye.uk/en/networking/protocol-helpers-turn-them-off/ Mon, 14 Sep 2026 09:00:00 +0100 https://blogs.damiendye.uk/en/networking/protocol-helpers-turn-them-off/ A NAT helper reads the inside of your packets and opens inbound ports on what it finds there. Anyone can write that text — a web page has been enough since 2010. How helpers work, how crafted packets turn them into a port-opening service for strangers, what IPsec pass-through does, why they fail Cyber Essentials, and how to switch the lot off.