It doesn’t matter if you are new to computer security or an expert, this section is for you. A firewall test checks your computer for ports that are commonly left open and that could allow your computer to be compromised, including open ports known to be used by malware.
If you are the typical home computer user surfing the net, a test should show no open ports facing the internet. If open ports are discovered, the next step is understanding what each port is commonly used for and how to lock it down – which is exactly what our port database is for.
What you can check right now
While our interactive port scanner is being rebuilt on modern infrastructure, you can already audit a lot about your exposure:
- Check your public IP address – the address any attacker would actually probe. If you’re behind a VPN or proxy, verify it shows the address you expect.
- Look up any port number – our database covers registered services, IDS rule references, and known malware activity for TCP and UDP ports, so you can identify what’s listening before you allow it.
- Review your digital footprint – see what every website can read about your connection and browser.
- Check your router’s port forwarding table – every forwarded port is a deliberate hole in your firewall. If you don’t recognize an entry, look the port up and close it.
Accuracy of firewall testing
Note that some high-end hardware firewalls (Cisco PIX and similar) and software firewalls may permanently block an IP address when they detect a port scan. When running any online scan, you’ll want to temporarily disable this autoblock feature (not the firewall) or you’ll receive incorrect results. For example, say you have a virus running on port 80 and your firewall detects and blocks the scanner’s IP address after port 50 – every port after 50 will appear closed to that scanner, while a real attacker starting their scan at port 80 sees it wide open. Many attackers probe specific ports at a slow rate precisely to evade autoblock features.
If you are on a private network, you may be connected through a router, proxy, or firewall, and any external test will be conducted against that device instead of your computer. For example: at a large company, you and everyone else in the office share the same external IP address – an online test audits the company firewall, not your PC’s. If you are unsure how your security is set up at work, do not run security scans, and never audit company infrastructure without your IT department’s permission.
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