Although you lose some effectiveness against malware with free antivirus, you do gain a little speed. The free products we looked at were faster on average than the paid products in 9 of the 12 speed tests we take into account. Again, the difference was slight--the largest speed difference was around 10 percent. Both free and paid antivirus increased system startup times: A test PC with no antivirus software installed booted up in 40.1 seconds on average. With free antivirus installed, the test system started up in 44.1 seconds on average; and with paid antivirus installed, startup times increased to 46 seconds. It's hard to pin down the exact reason for this difference, but again, the difference is slight enough that it's basically statistically insignificant.
Scan speeds, however, are a mixed bag. In our on-demand scan tests, paid antivirus programs edged out the freebies, scanning 4.5GB worth of files in an average of 2 minutes, 25 seconds. Free products, by comparison, completed the same test in an average of 2 minutes, 44 seconds.
Free and paid products were nearly neck and neck in the on-access scan tests, which show how quickly the software can scan files for malware when they're opened or saved to disk. Using the same 4.5GB of files, free products completed the on-access scan test in an average time of 4 minutes, 50 seconds. Their paid counterparts completed the test 8 seconds later.
Given how close the two classes of products are in terms of speed and effectiveness, the two biggest factors are features and customer support. With some exceptions, you get better customer support and more comprehensive security features with a paid product, but if you're willing to forgo these, it's definitely worth considering going free.
Which free and paid antivirus products are best for you?
Avast Free Antivirus comes out tops among free products thanks to its all-around strong malware-detection scores, good design, and low system drag. Avira AntiVir Personal takes second place: It put up solid malware-detection scores, but its interface is kludgy.
Norton Antivirus leads the paid-software pack owing to its excellent malware detection, very good interface design, and comprehensive feature set that includes file-reputation analysis, a cloud-based scanner (which can help identify new malware more quickly), and system performance analysis tools. BitDefender Antivirus Pro 2011 is a close second thanks to strong malware detection; but slow scan speeds and some interface issues prevented it from taking first.
Top Free Antivirus: Avast
Avast Free Antivirus couples good all-around malware detection with a speedy, well-designed package. We liked its easy installation process, smooth interface design, and minimal impact on system performance.
In traditional signature-based malware tests, Avast Free Antivirus detected 94.8 percent of samples, which is neither particularly good nor bad. It also did a decent, though not outstanding, job at detecting malware in our real-world malware detection tests: It completely blocked 76 percent of attacks (which is right about average), and partially blocked 4 percent of attacks.
But on the plus side, Avast Free Antivirus didn't falsely identify a single "safe" file as a piece of malware, the only free product we looked at that achieved this. Avast Free Antivirus also did a good job at disinfecting a PC; it removed all active components of malware infections 80 percent of the time, which set the pace among the free products we looked at.
Scan speeds are also very good. Its on-demand scan speed of 90 seconds was a close second to Avira AntiVir Personal, which completed the test in 87 seconds. And Avast Free Antivirus completed the on-access scan speed tests in 3 minutes, 40 seconds, tops among the products we tested.
Top Paid Antivirus: Norton Antivirus 2011
Norton Antivirus 2011 (US$40 for a one-year, single-PC license as of 10/26/2010) leads the pack of 2011 paid antivirus products. It does a very good job at detecting and removing malware, and has a smooth interface, although its speed is decidedly average.
Installing Norton Antivirus 2011 is a breeze: The well-designed installer only requires you to click through two screens before it begins installing. Norton Antivirus has a smooth, polished interface: The main screen shows on-off toggles for its various protection features, as well as a map showing the global cybercrime activity over the last 24 hours.
When it came to malware detection and removal, Norton Antivirus put out strong all-around scores. Norton Antivirus detected 98.7 percent of malware samples using traditional signature-based malware detection. This is an above average score, but it trails Panda Antivirus Pro 2011, which detected 99.8 percent of samples.
Norton also put up excellent scores in the blocking of real-world malware attacks: Norton completely blocked 24 of the 25 samples we threw at it, but it did miss one sample completely. Norton also detected all active infections in our tests; it removed the active components of an infection 80 percent of the time, and was able to completely remove the infections 60 percent of the time--both above-average scores.
Norton put up good scores in our speed testing, but not top-notch results. It completed an on-access scan of 4.5GB of files in 4 minutes, 32 seconds. This puts it ahead of the average of 4 minutes, 59 seconds, but it behind the top-performing product, which completed this test in 3 minutes, 35 seconds. Its on-demand scan speed of 2 minutes, one second is also above average, but again, it trails the top performing program by a good 30 seconds.