Normally, when your computer receives a connection request from another computer it lets the other computer know that this port is closed. In stealth mode, your computer will not respond, making it seem like it is not turned on or not connected to the Internet.
To switch Stealth mode on or off:
Select Options
Select System
Select Stealth in Answer type field to make your computer "stealth" or select Normal to make your computer "visible".
It is recommended that you keep Outpost Firewall in stealth mode unless you have some reason not to.