The best way to determine if your computer’s (or router’s) firewall is working and optimized is to effectively try to penetrate it. Browser-based utility ShieldsUP! tests your firewall for vulnerabilities and kinks in your computer’s defense.

After you give ShieldsUP! permission to run tests on your computer and choose a test type, it looks for weaknesses and openings that hackers and intruders can use to attack your machine. You can test in five different categories: file sharing, common ports, all service ports, messenger spam, and browser headers. When a test completes, ShieldsUP! will displays the results and offer suggestions for how you can improve your security, with detailed explanations. It’s a good tool for evaluating your computer’s security and determining whether you need to amp up your computer’s defenses.

We actually mentioned ShieldsUp! in passing in our previous guide to port-scanning your computer for security holes, but it’s a solid tool worth highlighting on its own. If your port-scanning interest has been piqued, be sure to check out our previous guide for a more thorough examination of the subject.