What are the issues to consider with personal firewalls?

No firewall is perfect. Personal firewalls are like any protection, if properly designed and properly configured, they can protect the PC from many attacks. However, they are software, and if there is a vulnerability in the code of the firewall and it is discovered, an attacker might use that vulnerability to break into your PC or attack it with a worm or Trojan. To make this risk less likely:

• Make sure to monitor the firewall vendor's Web site so that you can apply any updates to the firewall as soon as they are available.
• Make sure you understand how to properly configure the firewall. A firewall should block all traffic and then allow you to configure what traffic you want to allow.
• Keep the rest of your system and application software up to date. There are two reasons for this; first, if the firewall is compromised, then the software may not be vulnerable to the attack; second, firewalls cannot protect you from code you choose to run on your system. If you download a game or other software, it might contain malware. If you click on an attachment it might be malware.
• Be aware and act like you are. Malware can be introduced into your system if you visit sites and download it (you might do so without knowing it), click on an attachment or load infected software from a disk.
• Obtain and use an external firewall between your computer and the Internet.