Norton, Kaspersky, and Bitdefender Rule New Antivirus Test

Researchers at German lab AV-Test keep twenty-odd antivirus products under observation constantly, collating and reporting their results every couple months. They cycle between testing under Windows XP, Windows 7, and Windows 8, sometimes using 64-bit editions. The latest results, released today, relate to testing under 64-bit Windows 7. Some products scored much better than when tested under the 32-bit operating system; others lost points galore.
Three-Part Score
AV-Test assigns each product up to six points in three different areas: Protection, Performance, and Usability. To test Protection, they gather brand-new malware samples daily and note whether each antivirus identifies and blocks them, either by detecting the file's signature or by recognizing its malicious behavior. A detection-rate test using common malware also feeds into the Protection score.
The Performance rating is straightforward. The less impact a product has on system performance, the higher its score. Researchers time a number of common user activities with and without the antivirus active to calculate that impact. The activities include "visiting websites, downloading software, installing and running programs and copying data."
Usability doesn't refer to the product's user interface, but rather to possible problems antivirus protection might cause. Researchers visit hundreds of known safe websites and downgrade any product that erroneously blocks access to a site or warns that it might be dangerous. A product that identifies a valid program as malicious will likewise lose points, as will a product that displays erroneous warnings about a legitimate program.
Certification
In order to pass AV-Test's certification, a product needs a total score of 10 points or more, with at least one point in each of the three categories. All tested products did manage certification, though AhnLab and Norman squeaked by with a bare 10 points.
Because Windows itself includes antivirus protection, AV-Test doesn't list Microsoft Security Essentials as one of the tested programs. Rather, it's considered a baseline. A product that can't beat MSE is doing pretty poorly. With 9.5 points, MSE wouldn't have received certification.
Climbers and Sinkers
The test before this one was also conducted under Windows 7, but it was the 32-bit version. A drop in score between the two tests might identify a product whose 64-bit edition needs work. Norman and Kingsoft in particular lost fully 2.5 points between the 32-bit test and the 64-bit test.
Norton's designers don't approve of static malware-identification tests, and portions of the AV-Test suite do include static detection. I don't imagine they'll complain about this round of testing, though. Norton gained 2.0 points over the previous test, reaching an impressive 17 of 18 possible points. Kaspersky also took 17 points, while Bitdefender beat all the rest with 17.5 points.
Just like crash-testing for cars, independent antivirus testing lets you see how a product performs in a dangerous situation without having to enter that situation yourself.