Kaspersky Anti-Virus 2011 takes fifth place in our roundup of 2011 antivirus software, closely trailing fourth-place finisher G-Data AntiVirus 2011. It did a great job at stopping brand new malware attacks, and a reasonable--though not top-notch--job at detecting known malware, and it sports a well-designed interface. On the downside, its impact on PC performance was worse than average.

Kasperky features a highly streamlined installation process: You have to click through only two screens before installation begins. Once you install, you'll be given the option to activate it or run it in 30-day trial mode.

I found the main Kaspersky interface to be very well designed. The main window is clean, easy to read, and attractive, complete with a big, clear status indicator at the top of the window. The scan tab not only shows a progress bar for a scan, but also an estimate of how long the scan should take--a feature surprisingly absent from a number of antivirus programs I looked at. The scan tab also includes a "hot spot": Drag a file you want to scan to the hot spot, and Kaspersky will scan it for you.

Kaspersky Anti-Virus 2011 ($40 for one year on one PC, as of 11/23/2010) was an all-around solid performer in our malware detection, blocking, and cleanup tests. It detected 95.7 percent of known malware samples in tests that rely largely on malware signature files. This is a decent score, but the top performers on this test managed to detect over 99 percent of samples.

Kaspersky performed a little better in tests against live malware attacks designed to determine how well antivirus products can block brand-new malware. In this test, Kaspersky completely blocked 88 percent of samples, and partially blocked an additional 4 percent of samples. This is an above-average score, but not quite up to frontrunner status--the top scorer was able to fully block 96 percent of attacks.

When it came to cleaning up malware infections, Kaspersky held its own: It detected all infections on the test PC, and removed active malware components in 80 percent of cases, which ties the high score in this test. In addition, it removed all traces of infections in 50 percent of cases--a solid score.

Kaspersky was one of the better performers running running manually initiated on-demand scans: It scanned 4.5GB of files in 1 minute, 40 seconds. This trailed the fastest performer by only 13 seconds, and was well above the average scan time of 2 minutes, 21 seconds.

Tests for on-access scans--which determine how quickly antivirus software can scan for malware when files are opened or saved--were another story. There, Kaspersky completed the scan in 5 minutes, 10 seconds, which was slightly slower than average.

In addition, Kaspersky Anti-Virus 2011 caused a somewhat larger hit on overall system performance than most other antivirus packages we looked at. The test PC started up in 54 seconds with Kaspersky installed. This put it well behind the average startup time for the test PC with antivirus software installed (46.5 seconds), and it represents a nearly 14-second increase over the startup time with no antivirus software installed (40.1 seconds). Kaspersky slowed file copy and download tasks more significantly than other suites as well.

If system performance isn't a major concern for you, Kaspsersky Anti-Virus is well worth considering on the strength of its malware blocking capabilities and great interface. Otherwise, consider another product with a smaller impact on your PC's performance such as Avast Pro Antivirus 5.