"I just don't understand it!" Dave told me frantically over the phone. "We have antivirus software on our systems over here, yet we continue to get infected with viruses. We've spent hours and hours scanning our drives. What can we do?" Dave's predicament happens to many small and medium-size businesses, as well as to users running home networks. "Dave, when you say you have antivirus software on your systems, what exactly do you mean?" I asked.

"Well," he replied, "We're running either Norton Antivirus or McAfee on all our PCs."

"But what about your file servers, e-mail servers, and other things like scanning files that you might be downloading?" I queried. As it turned out, Dave's business had indeed installed virus-scanning software on its desktop machines. However, the software had been configured only to scan the hard drives of each PC weekly for viruses. Real-time virus scanning was not enabled.

As it was configured, Dave's antivirus protection was really almost no defense at all. Viruses were able to manifest themselves on Dave's systems and, through file sharing, continuously propagate themselves. In short, Dave's computing environment was seriously antivirus-challenged.

What about you? Do you only run antivirus software on end-user desktops? And how is that desktop antivirus software configured? Every company or home network will be slightly different, but at a minimum you need antivirus technologies that can work in real time to protect your network perimeter, servers, desktops, e-mails, and file transfers.

It is no longer safe to assume that virus writers will target only executable program files or send viruses as e-mail attachments. For example, recent efforts by virus authors have yielded virus strains that can be embedded in image files. This may potentially allow Web sites to become more easily infected.

In addition, you might get the impression from news headlines that viruses are limited to the Windows platform and other Microsoft technologies, such as Outlook and Internet Information Server. Though Microsoft technologies are widely targeted by virus authors because of their popularity and because of the way the software is constructed, there are viruses targeted at most major computing platforms and several viruses out there that are even targeted at handheld and wireless devices.

In your face

Not that long ago, you could generally select antivirus tools for the desktop on the basis of cost and their ability to catch the greatest number of viruses before they could infect you. These days, those arguments are still important. However, costs have come down (roughly $10 to $50 per desktop, depending on how many licenses are purchased) and virus detection technology is now fairly comparable across all of the desktop tools available.

So what else is important to consider? Obviously, if you are running desktop platforms other than Windows, you need to be certain that your platform is supported. For example, if you use Mac OS X, you'll want to examine Norton Antivirus for Macintosh or other commercial or open-source antivirus tools for the Mac.

Next, be sure you have configured each desktop to scan in real time. This means if you receive e-mail or download a file, the virus scanner will examine your activity and detect (and deflect) the virus before it can affect your system. Real-time virus checking is also available for Web browsers and for file operations, such as opening a document with StarOffice or Microsoft Office.

Centralized management capabilities are especially useful for businesses. All four of the vendors I looked at recently offered the ability to manage antivirus software centrally. This is important if you have more than just a few machines, because it means you can maintain antivirus software on all your machines with only one set of actions.

For example, you can refresh all the machines at your company with the latest antivirus updates in one fell swoop. Or you might schedule automated hard-drive scans on all systems from the management console. Equally important, the management console lets you manage antivirus tasks on desktops that may physically be located in your office or in an employee's home office.

When I looked at the systems at my friend Dave's business, I noticed one thing that many desktop users forgetÑantivirus updates. Dave told me that they just hadn't gotten around to it. Mistake! Systems that aren't kept up to date with the latest antivirus information pose a threat too, as new viruses are released into the wild daily.

All of the solutions I examined offered automatic updates. You must configure the update interval and I usually set my tools to check for updates daily. Note that some automated update procedures require a subscription, which usually costs $7 to $10 per year above and beyond product purchase.

On the server side

Many of the same things you consider when thinking about desktop antivirus tools apply equally well to the server side of your business or home network. For example, whether you use Windows, Linux, FreeBSD, Solaris, NetWare, or some other operating system, you need server-side virus protection.

As with the desktop, real-time virus scanning of file servers is definitely recommended. For example, I configure my server-side antivirus tools to check both incoming and outgoing files of all types. This introduces a small bit of overhead, but network performance is only minimally impacted. Had my friend Dave configured his file systems in the same manner, he would likely not have struggled so hard trying to eliminate viruses.

On the server side, all four of the vendors I examined offered comparable support, though Trend Micro and Symantec products are easier to install and configure than those of McAfee and Panda Software. In particular, I liked Trend Micro's new Server Protect for Linux because of its easy setup and browser-based configuration. I was able to configure and launch virus scans locally and remotely (with authentication) as well as enable real-time scanning.

Most server-side virus technologies can also plug in to the centralized management tools provided by the antivirus vendors. If you operate a business with many systems or more than one location, I highly recommend using the centralized tools to manage antivirus tasks on both servers and desktops.

Beyond file servers, you may want to use servers for other purposes, such as groupware or portal activities. If you use Lotus Notes or Microsoft Exchange, you'll want to examine antivirus tools that are available specifically for these products. For example, McAfee offers its GroupShield Exchange and GroupShield Domino, while Panda Software has PAV for Notes/Domino and PAV for Exchange.

One of my e-mail accounts is hosted on a Domino server running McAfee's GroupShield for Domino, and I'm very happy with the level of antivirus support to date. As with desktop and server antivirus technology, automating antivirus updates and real-time scanning for groupware products are must-have items.

Finding antivirus solutions that support specific portal technology can be a bit dicey. Trend Micro offers its Portal Protect, but it is limited to Microsoft's SharePoint Portal server. If you're purchasing or using a packaged portal solution, check with your portal provider to make sure your portal server can be protected from viruses.

The network and beyond

What else might you have on your network aside from the file servers, portals, and groupware systems that should be protected? Given the growth in data we've seen over the past decade, many businesses and some home networks may now include either storage area networks (SANs) or network attached storage (NAS), and these may be used to back up server data or store historical information, such as customer purchases over time.

Antivirus technologies are also needed on SANs and NAS devices. In many instances, the same antivirus technology you apply to file servers can also be used on NAS devices. But some SANs require vendor-specific antivirus technology. As with portals, check with the supplier of your SANs or NAS solution to see what antivirus tools they recommend. Certainly, you don't want viruses hiding out in long-term storage areas any more than you want them on your desktops or servers.

There are still other areas on your network where you should consider adding antivirus technology. For example, if you use any kind of network appliances you'll want to be sure they are checked for viruses in real time and updated with the latest antivirus data. Some antivirus vendors, such as Trend Micro, are offering tools to help in this area.

What about the outward-facing parts of your network? Do all the systems in your business or home network connect to the Internet via a gateway device of some sort? Do you operate a Web server that is publicly accessible? All four of the vendors I evaluated offer antivirus tools that support gateway systems and Web servers.

Gateway and Web server antivirus technologies are some of the most important to implement. If you are able to deflect a virus at your gateway, you'll likely reduce the chances of internal servers and desktops becoming infected. Likewise, if you protect your Web server, visitors to your site probably won't become infected after interacting with it.

Two other interesting antivirus technologies are protection for wireless and handheld devices and the availability of online virus scanning. McAfee, for example, offers antivirus tools for Palm, EPOC, and Pocket PC devices. Meanwhile, Trend Micro offers its HouseCall service, which enables users to scan their systems for viruses via the Web at any time.

All four of the vendors I evaluated offer useful tools that can protect various parts of your computing environment. Of the four, I find Symantec and Trend Micro to be the best in terms of the width of solutions offered and ease of use. McAfee and Panda Software are a close second.

As my friend Dave learned, properly configured desktop antivirus tools are vitally important, as is the need to implement antivirus technology throughout your computing environment. This is a good time to consider if you are protecting all of your desktops, server-based systems, and other computing assets in real time while also automatically updating your antivirus software.