Malware protection. Anti-virus software on a Windows netbook isn't an option -- it's an IQ test. The only question you need to ask is whether it comes pre-installed or if you'll have to install it yourself.

There is less agreement on the need for Linux anti-virus software. Many Linux users don't see any need for the stuff, and the numbers bear them out: There are very few Linux viruses in the wild, and fewer still capable of doing serious damage.

Still, I understand that some netbook vendors do ship Linux models with anti-virus software included. If you're the risk-averse type or if your business has strict anti-malware policies in place, then rest assured that quality Linux anti-virus software is available, either from commercial software vendors or as free, open-source software.

Software updates. Installing regular OS and application software updates is another no-brainer. Skipping security updates on any system, whether it runs Linux or Windows, creates security holes that grow bigger -- much bigger -- over time. The same applies to application updates, especially those involving Web browsers or other network-aware apps. Windows users can and should get OS updates automatically from Microsoft. Other applications, such as Web browsers, typically have their own update alert features. This routine can vary somewhat for Linux users. A major distro like Ubuntu, for example, typically offers automatic updates not just for the OS but also for Web browsers and many other third-party applications. Some netbook vendors, however, use customized Linux distros that may or may not offer similar comprehensive software-update tools. If you pick a Linux-based netbook, be sure that you understand how its software update tool works and what applications are included in any automatic update alerts. If some applications, such as a Web browser, aren't automatically updated, then configure the application itself to download and install its own updates whenever possible.

Firewall and access-control software. Every current version of Windows XP includes Internet Connection Firewall (ICF) as a built-in component. ICF isn't as feature-rich as many third-party firewalls, but it serves its purpose: Protecting your computer against unauthorized outside access. The security of a Linux system against outside attacks can vary a great deal, depending mostly upon its default configuration. A properly locked-down Linux netbook might be fairly well protected, while an improperly configured system can be a lot more vulnerable. Once again, it is important to understand how a Linux netbook handles network security. Does it include a built-in firewall? Does the firewall offer a graphical interface or other tool for managing access, or does the vendor assume that users will not (or should not) change its default configuration? How does the firewall deal with wireless versus wired-network security? These are simple questions, and any competent netbook vendor or reseller should be able to answer them quickly and clearly. If they can't, then take your business to someone who can.