This is not really a tweak, but simply a list of websites, which offer online system security testing. If you have a firewall, you can see now if it's secure enough.

Remember, hackers always find a way into your system if they want!

http://grc.com/

http://hackerwhacker.com/

http://scan.sygatetech.com/

http://www.testmyfirewall.com/

http://www.auditmypc.com/

http://www.iggyz.com/Test.html

http://online.securityfocus.com/cgi-bin/sfonline/links.pl?cat=43&offset=60

There are more, but I think this will be sufficient at the moment. Happy testing!