An extremely useful, famous and popular site which offers a free
basic test of your firewall by attempting to connect back to the
computer you connect from. Very useful for detecting potential
Scroll down, click "Shields Up!" logo, then click "Test
My Shields" (basic test for external filesharing a.k.a NetBIOS
a.k.a. Samba access) or "Probe My Ports" (checks most
common ports of your firewall. Tests generally take less than
10 seconds due to their new ideas on TCP/IP connectivity.
Also a helpful collection of firewall / TCP/IP related technical
information, explained in detail.