Some time ago I blogged about the excellent Skype Blackhat presentation. Now you can read on Heise how Skype bypasses NAT and firewall, something that is rather trickey with open standards VOIP protocols.

How Skype get round firewalls

But anyone who has used the popular internet telephony software Skype knows that it works as smoothly behind a NAT firewall as it does if the PC is connected directly to the internet. The reason for this is that the inventors of Skype and similar software have come up with a solution.