by Kp » Tue Jul 04, 2006 12:18 pm
It's an iptables target that checks whether there's an application listening on the desired port. If an application is present, the target behaves like ACCEPT. If there's no application listening, the target behaves like DROP. It's useful if you want to expose a server that's not always running, but not make yourself visible to a portscan when the server's not runninig.