At the 21C3 Maik and I did a presentation on how you get your packets through packet filters. Further, the presentation showed an overview of packet filters and application layer gateways. Tools like ssh, socat, httptunnel and so on were introduced.

The more advanced part showed how to use the DNS or icmp packets. Maik coded an icmp-tunnel application. Unfortunately, just the day of the presentation it did not work. As always. Our ambition in finishing up that application was cooled down when we found this implemenataion called ptunnel.

The presentation originated from a "Themenabend" at the c3d2.