This article is a little old now but I imagine the basic technique is still the same: http://www.h-online.com/security/features/How-Skype-Co-get-round-firewall

This article is a little old now but I imagine the basic technique is still the same: http://www.h-online.com/security/features/How-Skype-Co-get-round-firewalls-747314.html http://www.h-online.com/security/features/How-Skype-Co-get-r... As I understand it, for corporate firewalls or routers/firewalls configured to not allow "hole punching", Skype will use the supernode as a relay for all communications.