AS WE DESCRIBED in the first article in this series, these days it's possible to kit out a Windows computer with a fairly complete set of Internet and productivity tools and utilities completely for free. Not only can this save you a fair bit of cash, there are other benefits – not least of which is security. Even if you know your stuff, have a read - you might find some useful tips.

Keeping the yobs out
A firewall is an absolute necessity. The Internet's a hostile place. An unprotected Windows machine connected to the Internet will be infected within seconds to minutes.

If you use a separate router, connecting your PC to the Internet via an Ethernet cable, chances are that it contains a firewall and you're fairly safe. If, on the other hand, you use a modem to connect - including most USB ADSL modems - you're at risk. XP and Vista sport built-in firewalls, which aren't the most sophisticated around but which do the job. If you're on Windows 2000, though, you need an additional third-party one.

The snag with both hardware firewalls and XP's built-in one (and Vista's in its default basic mode) is that they only block inbound access, from the Internet to your computer. If a program running on your machine wants to make an an outbound connection to a host on the Web, it just happens, silently. This is a powerful argument for using a third-party replacement instead, even if you have a router.

Tip: if you're on a LAN, stick with Windows' built-in firewall. Add-on firewalls can block access to your network devices and servers, which is a pain, and most don't play well with Internet Connection Sharing. But if you're using that, do yourself a favour and buy a router.

Probably the best-known software firewall for Windows is Checkpoint's ZoneAlarm. Like many of the free downloads from commercial companies, Checkpoint doesn't exactly shout about the free version, and legally you can only use it for home and non-profit or charity purposes. It also tends to nag you to get the full, commercial version, which includes anti-spyware and other features.

Less intrusive, with both a good reputation and no riders about commercial use, is Comodo's free Personal Firewall.

Only one software firewall at a time can run; installing a third-party one disables the Windows firewall and takes over. After a reboot, you'll spot the difference: the first time you run any app that connects to the Internet- browser, email, etc. - the firewall will block it and ask you if it's allowed out. With some firewalls, this occurs for each type of connection, and again when the relevant application is updated to a newer version. So long as you tick the box that tells the firewall to remember your answers, this only happens at first and it will soon stop. After the initial training period, any new requests for external access are the firewall doing its job. If you haven't added anything new, this might mean that some unnoticed bit of malware is trying to phone home. Treat unexpected alerts with suspicion.

What a software firewall won't do
A firewall alone isn't enough; you need antivirus and antispyware too. The next couple of articles will look at what's available for free in those departments.

Some paid-for "security suites" will do some or all of these functions in one program, but there are advantages to keeping them separate. If you have one program that's doing everything and it dies or gets taken out by a new bit of malware, that's it – all your protection disappears. With multiple separate tools running independently, even if one goes, the others keep working. You don't lose all your protection in one go. Given that all the parts can be had for nothing, the partwork approach saves money, too.

One snag is that multiple discrete programs will take up more of the resources of your computer, but it's not a massive load. Plus, of course, you have to learn to operate each one. Most free security tools are much more lightweight than the big commercial offerings, though, and won't slow your PC down as much, as the marketing department hasn't burdened them with extra features for more ticks on the packaging.

Other candidates
ZoneAlarm and Comodo aren't the only freebies. PC Tools also offers a suite of protection tools gratis, with no restrictions about commercial use. Sunbelt's Kerio Personal Firewall has a good reputation, but only runs with all its features for thirty days, then drops down to a less-functional mode. However, even its free mode is better than nothing.

German vendor Ashampoo offers a whole host of free and inexpensive programs, including a version of its firewall. R-Tools Technology is best known for R-Studio, its data recovery tool for damaged NTFS drives, but it offers a free firewall as well, R-Firewall.

On the open source front, offerings are rather more basic, and several projects seem to have been abandoned years ago. TCP/IP experts can get WIPFW, a port of the FreeBSD "ipfw" tool. Microsoft's open source project site CodePlex offers NetDefender, and curiously named Chinese company Filseclab makes the source of its Personal Firewall 2.5 available.

There are lots of no-cost software firewalls available; this isn't a comprehensive list. Let us know if you think there's something we missed that ought to be here! µ

L'Inqs
ZoneAlarm from Checkpoint
Comodo Free Firewall
Firewall Plus from PC Tools
Kerio Personal Firewall
Ashampoo Firewall requires registration, resulting in (unsubscribable) promotional emails.
R-Firewall from R-Tools Technology

Open source offerings
WIPFW
NetDefender
Filseclab