For scan your network holes:

Leak Testers:

LeakTest - http://grc.com/lt/leaktest.htm
TooLeaky - http://tooleaky.zensoft.com
Firehole - http://keir.net/firehole.html
Yalta - http://www.soft4ever.com/security_test/En/index.htm


Online Port Scanners:

Sygate – Option in software menu.
Symantec - http://www.symantec.com/cgi-bin/securitycheck.cgi
PC Flank - http://www.pcflank.com/index.htm