Host-Based Firewalls

Host-based firewalls are software firewalls installed on each individual system. Depending on the software you choose, a host-based firewall can offer features beyond those of network firewalls, such as protecting your computer from spyware (a component of some free software that tracks your Web browsing habits) and Trojan horses (a program that claims to do one thing, but does another, malicious thing, such as recording your passwords). If you travel with a laptop, a host-based firewall is a necessity—you need protection wherever you connect to the Internet, and your hardware firewall can protect you only at home.

Why would you buy third-party firewall software when Windows XP includes ICF for free? ICF is designed to provide basic intrusion prevention, but doesn’t include the rich features of a third-party firewall application. Most third-party firewalls protect you from software that could violate your privacy or allow an attacker to misuse your computer—features not found in ICF. Also, you can install third-party firewall programs on systems that have older versions of Windows. Note that firewall software doesn’t replace antivirus software. You should use both.

Popular host-based firewall products include ZoneAlarm, Tiny Personal Firewall, Agnitum Outpost Firewall, Kerio Personal Firewall, and Internet Security Systems’ BlackICE PC Protection. Most host-based firewall software is available in free or trial versions, so it won’t cost you anything to download these packages and determine whether they meet your needs better than ICF.