IDENT, ZoneAlarm, and ShieldsUP!

Even though your computer's web browser already has a relationship with the web server at GRC, our tests originate from a different "foreign" IP address. ZoneAlarm therefore drops incoming packets to port 113 from this different probing IP address and ZoneAlarm users see that port 113 is stealthed to passing Internet scans.

To demonstrate how ZoneAlarm (and perhaps someday other firewalls or NAT routers) selectively "unstealth" port 113 — but only for known "friendly" machines — we simply initiate a connection from your web browser to the ShieldsUP! scanning IP. Even though the connection attempt will ultimately fail (since there's no web server at the probing address), ZoneAlarm will note the outgoing attempt and will unstealth port 113 for subsequent probes.

Step One: Verify that our scan currently show port 113 stealthed. (You may wish to use one of the other remote port tests which will be faster than an entire 1056-port grid scan.)

Step Two: Open a secondary web browser window to initiate a connection to the probing IP. (Users of Microsoft Internet Explorer can press Ctrl-N to "clone" their current browser window.)

Step Three: In the secondary web browser window, click this URL or enter this address:

http://4.79.142.206

This second connection attempt will ultimately fail, but ZoneAlarm will notice the effort, which is all that's necessary.

Step Four: Finally, refresh the port probe window or repeat the scan to check your system's current port status. You should find that port 113 is no longer "stealth" to the probing IP address because you are attempting to connect to it and it has been determined to be "friendly".

Step Five: If you're curious, stop and close the secondary web browser window and periodically refresh your port probe window to see how long the "friendly" status persists before Zone Alarm returns the probing IP to unknown status and port 113 to full stealth.