I read tonight for the first time about Port Knocking. Seems Linux users have a way to keep the firewalls closed for a specific port unless the connector has the correct passcode by detecting connections to closed ports. So if you are running a FTP site that you want to keep under wraps but want to be able to access it when you need it port knocking is a way to keep the port closed to nosy unwanted visitors. [Boing Boing] [www.linuxjournal.com]