Step 4: Set up a firewall

Using a properly configured firewall is a required step in ensuring computer security.

What is a firewall?

When properly configured, a computer firewall protects your computer from intruders who exploit flaws in your computer's software to create annoyances or to steal or damage your data.

A firewall is not the same as anti-virus software or anti-spyware software -- it's best if you have all of these since each protects your computer in a different way.

Why do I need a firewall?

If your computer doesn't have a properly configured firewall, it could:

• spread viruses to people listed in your address book
• allow intruders to record your keystrokes or view or delete your data
• allow intruders to send spam from your computer
• execute distributed denial of service attacks on other computers

-- all without your knowledge.

Intruders can gain access to your computer through your computer's open network ports, which are communications channels for programs. A firewall can secure any ports which might be open on your computer.

More information: How Firewalls Work and Frequently Asked Questions About Internet Firewalls.

To determine how to set up a software firewall, what operating system does your computer have?

Test your firewall

1. Test that the firewall protects your computer by visiting one or more of the following test sites:
   1. ShieldsUp!
   2. Sygate Online Services
   3. the Security Scan feature of Symantec Security Check
   4. LeakTest
2. If your firewall is protecting your computer, congratulations! Proceed to Step 5: Install operating system updates.

Help? Feedback?

Try asking your question in the Craigslist computer forum. To provide feedback for this page, send the URL and your comments to Web & Data Services Manager Frank Farm at farmf@pharmacy.ucsf.edu.

Go To: Computer Security