By installing a few extras with BackTrack 5 (another tool-set that penetration testers know well) it is possible to run a script based upon Metasploit that generates a "reverse TCP payload". In essence, all of your Internet data is carried using a protocol called TCP/IP, where the IP part gives the "addresses" of the sender and receiver, and the TCP part ensures that the entirety of the data is reconstructed correctly once received as it is chopped up into small "packets" for transmission across the Internet. This "reverse payload" method means that you receive the unwanted data without realising it. Hence, it will bypass detection by the types of traps to are usually employed to capture unwanted code.It's such a shame that these tools are used in this way. Or is it? Perhaps that's the very reason they exist. After all this has shown a vulnerability and a form of attack vector that may not have been thought about by the AV and Firewall vendors.