pwnat, pronounced "poe-nat", is a tool that allows any number of clients behind NATs to communicate with a server behind a separate NAT with *no* port forwarding and *no* DMZ setup on any routers in order to directly communicate with each other. The server does not need to know anything about the clients trying to connect. Simply put, this is a proxy server that works behind a NAT, even when the client is behind a NAT, without any 3rd party.
WaterRoof is an IPFW firewall frontend for Mac OS X with a easy interface and many options.
ein weiteres protokoll um NAT zu piercen
STUN kommt auch bei xmeeting zum einsatz
psad is a collection of three lightweight system daemons (two main daemons and one helper daemon) that run on Linux machines and analyze Netfilter log messages to detect port scans and other suspicious traffic.