How do I know whether my computer is secure ?
If you don't use a firewall (or a NAT router with firewall features), don't have an Anti-virus and anti-spyware software, chances are your system is vulnerable to some attacks.
The most basic way to find out where your system is vulnerable (what ports are open) is to run our security scan. It will give you an idea of potential weak points.
The next logical step would be to read our Security articles to get a better understanding of the potential security issues and any possible countermeasures. Check the Security forum and read/ask questions. You might also want to check some of our hardware firewall/router reviews if you feel you know what you're looking for.