Malicious programs come in a huge variety of different types. Viruses spread from computer to computer by infecting other programs. Worms spread by exploiting capabilities of the network. Trojans pretend to be useful and valuable programs…until they turn and do something nasty. Adware's pop-up ads interfere with your work. Spyware can steal personal information while keyloggers steal everything you type, and more. Rootkits subvert the operating system to hide their activities. Scareware pretends to be security software but at best does no good. Which of these should your antivirus remove? Simple-all of them! Viruses make up only a small part of threats "in the wild," but the term antivirus has come to define protection against all types of "malware"-a term that hasn't gotten much traction outside the security industry. When most people talk about antivirus software, what they really mean is anti-malware software, and that's how I'm using the term here, too.

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MoreA full-blown security suite is the best protection against the gamut of security threats, as it combines antivirus protection with a firewall and other protective components. Still, many users prefer to build their own protective suite from separate best-of-breed components. Here's a run-down of your choices for standalone antivirus utilities.

Spyware Doctor with AntiVirus 2010, our Editors' Choice for for-pay antivirus, is the star player in the security lineup from PC Tools. In my hands-on testing, it holds the top scores for both malware removal and malware blocking, even beating out previous champion Norton Antivirus 2010 (though Norton remains the rootkit removal king). PC Tools Internet Security 2010 offers this same level of protection plus antispam, firewall, antiphishing, and a browser protection toolbar.

Avast! Free Antivirus 5.0 includes the same anti-malware protection found in company's full suite, avast! Internet Security 5.0. However, its protection level is more on par with the better free products than with the best suites or standalones. Yes, the best commercial products are significantly more effective than the free products. Avira AntiVir Personal 10 is also free for personal use. McAfee AntiVirus Plus 2010 offers the same protection found in McAfee Total Protection 2010, though neither of these is free. All of these products are significantly better at keeping malware out of a clean system than at cleaning up active malware on an infested system. AntiVir in particular left a number of rootkits and other threats actively running after its alleged removal.

Sunbelt Software's VIPRE Antivirus 4.0 outscored all but the very best of its competitors in my testing, and it includes some bonus features more often found in suites than standalone antivirus products. Sunbelt's own suite, VIPRE Antivirus Premium 4.0 adds little to the antivirus-just a firewall and a malicious website filter.

Unlike the pairs of products mentioned so far, AVG Anti-Virus Free Edition 9.0 and AVG Internet Security 9.0 offer different levels of malware protection. The free product scored significantly lower than the suite for both malware blocking and malware removal, and also scored lower than several other free antivirus solutions. Microsoft Security Essentials, another free solution, offers average protection against most sorts of malware but is especially weak against rootkits and commercial keyloggers.

Panda Cloud Antivirus Free Edition 1.0 and Trend Micro HouseCall 7.1 don't have a direct link with their related suites (Panda Internet Security 2010 and Micro Internet Security Pro (version 3)). The free Panda standalone, PCMag's Editors' Choice for free antivirus, scored noticeably better than its sibling suite in my malware blocking test, tying with Spyware Doctor. HouseCall, on the other hand, wasn't as effective at malware removal as the Trend Micro suite, and it doesn't include real-time malware blocking at all.

Not every antivirus product forms the center of a corresponding security suite. IObit Security 360 distinguished itself by scoring lowest or second-lowest in all of my tests-avoid it. Double Anti-Spy Professional relies on two anti-malware engines but its performance against malware was just decent. However, it scored better than all others at removing commercial keyloggers and preventing their installation, even those that use rootkit technology to evade detection. Ad-Aware Pro 8.1 brightened up my testing day by scoring better than all the rest at removing sneaky scareware programs that masquerade as valid security solutions.

If your aim is to build the perfect best-of-breed combination rather than seek the ultimate pre-packaged suite, you're sure to find a top choice among these products.

See a comparison chart of these products.

Ad-Aware Pro 8.1

$39.95 Direct

Ad-Aware Pro just keeps getting better. Version 8.1 introduces new malware-fighting technology, and the new Simple Mode is a boon for less-technical users. There are better products in the anti-malware category, but not many.

avast! Free Antivirus 5.0

Free

The new user interface of avast! free antivirus makes it easier to use, and its new technology eliminates more malware. This tool offers more control over settings and more detail in reporting than some of its free competitors.

AVG Anti-Virus Free Edition 9.0

Free

AVG believes everyone deserves free basic protection against Internet threats. The company's free antivirus offers that protection, and it's better than Microsoft's free product. Of course, the best for-pay anti-malware tools are even better, but not everyone can afford to pay.

Avira AntiVir Personal 10

Free

Avira AntiVir Personal does a great job keeping malware from infesting your clean computer system. Just don't rely on it to clean things up if the system is already infested. In testing, even when it did detect entrenched threats it often couldn't remove them.

Double Anti-Spy Professional

$29.95 (direct)

This product's two antivirus engines double its detecting power, but it doesn't clean up as well as it detects. It's as big and slow as using two separate products would be. On the plus side, the two engines don't conflict, and you only have to pay for one product.

IObit Security 360

Free

IObit Security 360 installs and scans quickly. The problem is, it just doesn't do the job of removing malware or preventing malware installation.

McAfee Virus Scan Plus 2010

$39.99 (direct)

McAfee AntiVirus Plus 2010's user-friendly new interface is a welcome departure for McAfee. On clean systems, it's great at blocking malware. Installing and running it on infested systems can be tough, but McAfee offers tons for such problems.

Microsoft Security Essentials 1.0

Free

Installing the free Microsoft Security Essentials will protect your system from malware—to a degree. But you'll get better protection from one of the other well-known free anti-malware products.

Norton AntiVirus 2010

$39.99 Direct

Norton AntiVirus 2010 is good at cleaning up malware and even better at protecting a clean system. Its Quorum and SONAR 2 technologies help catch zero-day threats. And its built-in self-repair systems let it install and run on most malware-infested systems. Just be wary of tech support agents trying to sell you expensive malware cleanup services.

Panda Cloud Antivirus - Free Edition 1.0

Free

Panda Cloud Antivirus offers free malware protection in a lightweight package with an ultra-fresh user interface.

Spyware Doctor with AntiVirus 2010

$39.95 (direct)

Spyware Doctor with AntiVirus 2010 adds numerous new "guards" against malware and promises enhanced malware detection and cleanup—and delivers. This product, our new Editors' Choice, broke records in my malware-removal and malware-blocking tests.

Trend Micro HouseCall 7.1

Free

Trend Micro's HouseCall gets to work quickly and uses a cloud-based malware database to find viruses and other threats. It's great for a second opinion alongside your existing solution because it doesn't run in the background when not scanning. That lack of real-time protection also means it shouldn't be your only anti-malware solution.

VIPRE Antivirus 4.0

$29.95 Direct

VIPRE is a very good standalone antivirus tool that outscores all but the very best of its competition in my tests. Those with more than three computers will love its $49.95 unlimited home license.

Please note: This is an ongoing roundup; we'll be adding more reviews throughout the year. If your favorite antivirus app isn't here, don't panic—it's not a conspiracy. We either haven't gotten to it yet, or we're waiting for a new version to be released.