Posted 10 August 2010 - 02:41 PM
I'll try to do this in order of the questions:
1. The Leak test only tests the firewall.
2. I don't find the ones that are downloaded useful. You have to allow them to run, which automatically (usually) makes firewall rules for them, and defeats the purpose of the test.
3. With most good up to date firewalls, it probably isn't needed. Unused ports are stealthed, and if you restrict your firewall too much, you may not be able to connect. Most firewalls are configured for safe access, and maximum security.
4. I'm sure it is safe to use any of the tools on Matousec's site. They may show as malicious because of the nature of the tool. It is trying to do something that your antivirus and firewall disapprove of.
5. If you connect to the internet via a router, the results may not be accurate anyway. The NAT router hides your presence on the internet, and uses a public IP address. Many of these types of tests give you results on the router firewall instead of on your own firewall.
To stay safe, use a good security suite with a two-way firewall, keep your browser updated, keep all vulnerabilities patched, avoid clicking on links even in what seems to be a safe web page. A NAT router if you have one is a very good first line of defense.