Excluding Firefox and its 400 million downloads and 120 million regular users, the days of a killer free application dominating hearts and minds are deader than Pets.com. Yet a single malware destroyer is what we're all hoping for, especially since malware and virus threats are as chameleonic as their intentions are devious.

Three antimalware applications have made it to the top of my list: Avira Antivir, AVG Anti-Spyware, and A-Squared Free.

These antimalware applications are a real challenge to parse through. Unless you've got a machine you're willing to risk wrecking, a disc loaded with digital nasties to replicate an infected environment, and a case of paracetamol--that's for you, not the computer--there's no surefire way to see just how well these things work until something bad gets through.

Antivir is the most complete program in the group, incorporating both antivirus and antimalware capabilities. Although AVG puts out a high-quality, popular, and free antivirus, it's a separate program. Antivir is loaded with features that other programs often make available only in their paid editions.

Antivir\'s main panel uses tabs and drop-downs to make navigation uncluttered. (Credit: CNET Networks Inc.)

Besides the usual battery of scans, it has a real-time Guard that starts working before it's even finished the first system scan, a rootkit detector, seven preloaded scans to simplify common checks--only removable hard drives, or only the Windows system folder, for example.

Most surprising about the Guard is that it didn't cause any system sluggishness, and even surprised me when it popped up with a randomly-found minor infestation on one of my machines. The Scheduler is as fully-formed as the other system features, so you can set not only when scans should begin but also when the program downloads new definition file updates. The in-program help was good, if not great, but bolstered by a useful mouse-over feature that beginners should find informative.

However, Antivir is no panacea. The Complete System scan can take hours, so unless you preset it to respond to threats with either the quarantine or deletion, it will wait for end-user input. The update process was also torpid, and sometimes required manual updates of the definition files. Fortunately, Avira seems to have anticipated this by placing concise manual-update instructions on its Web site.

Anti-Spyware is more complex than its AVG Anti-Virus cousin, and it's not for the casual enthusiast. Besides the Scanner, which offers an uncluttered customizable scan, scans limited to the registry or memory, and two prebuilt "fast" and "complete" scans, the Resident Shield blocked all malicious components I tried to install. Scanning options also let you choose to scan only compressed files, opt out of a heuristic analysis, and more.

AVG Anti-Spyware\'s Status page. (Credit: CNET Networks Inc.)

The overall level of security the application provides was also impressive. There are certain presets for programs that are known for creating security holes, such as Internet Explorer, there's a built-in Process Manager, and there's even a shredder that offers Fast, Secure, and Paranoid levels of deletion. Some of these tools might become disabled once the 30-day trial ends.

There are more than a few diagnostic tools to manage, from running processes to start-up entries to proxy connections--but the program provides little information as to which items are potentially dangerous. In some cases, the program hogged an inordinate amount of memory when its real-time shield was active and made even basic tasks mind-numbingly slow. Still, if you're very familiar with AVG Anti-Virus and you don't mind disabling the shield, AVG Anti-Spyware might be the tool you're looking for.

A-Squared Free has the lightest footprint of this trio, which makes it quite appealing for that reason alone. The main page mirrors the other programs also, as a sensible trailhead to delve into the application's deeper functions.

The main screen of A-Squared Free 3. (Credit: CNET Networks Inc.)

On the surface of it, A-Squared seems to have fewer features. But on the Scans page, if you check off the Manual Scan you get access to a diminished-yet-similar range of options. Heuristics, active malware, infected compressed files, and more can all be checked. The A-Squared knowledge base and help forums looked well-trafficked, and you can submit a suspected malware file to the publisher for examination.

The prebuilt scans--Quick, Smart, Deep--are fairly pedestrian sounding, but information as to how they were different was lacking. Obviously, Quick Scan is the fastest and most superficial, while the Deep Scan can take several hours depending on your machine size, but beyond a short one-sentence explanation next to the option, "Smart Scan: Good and fast result, but only important folders will be scanned," it was hard to parse.

If you choose a scan that examines your cookies, the application will recommend closing your Web browser--that's something you should be doing anyway, but the reminder is helpful. Custom lets you choose not only which folders to scan, but also lets you opt out of heuristic, tracking cookie, and spyware remnant scans. There is also a Whitelist where you can add folders or files, accessible at the bottom of the main Scan tab panel.

There's an annoying design quirk, where important options like the Whitelist are placed in the bottom left of the active panel, making them hard to see. It would also be nice to see scheduling options and real-time scanning, although that last one's resource-heavy. Although its easy to use, compared to AVG Anti-Spyware and Avira Antivir, A-Squared Free looks best as a backup.

Discuss your favorite antimalware scan-and-remover in TalkBack below.