Practically all suites offer some method to prevent malware from downloading through your browser without your consent. For example, a Website might pop up a fraudulent warning that your PC is infected and that you must buy a particular (but fake) antivirus program to remove it. Or it might trick you into downloading Trojan horses disguised as the latest version of Adobe Reader or Flash. Most security suites now monitor browser downloads and filter out this bogus software.

Comodo Internet Security 2011 Complete (which did not capture a spot in our Top 10 chart--click on the thumbnail at left) and the Kaspersky and Norton suites offered the best detection in our "real world" malicious downloads tests, which gauge how well the various suites block brand-new, as-yet unknown malware. And Norton Download Insight, which filters bad apps, now supports the Chrome, Opera, and Safari browsers (and AOL) as well as Internet Explorer and Firefox. Download managers from other companies typically work only with IE and Firefox.

Improved from last year is Norton Insight, which measures the relative trustworthiness of the files loaded on your desktop. The idea is that crowd-sourcing safe files (letting consumers around the world rate a file's safety) is better than white-listing them (depending on a static list of acceptable files).

Crowd-sourcing is also behind so-called cloud-based detection of new malware. Security software reports suspect new files from a PC to the cloud and creates antimalware signatures as needed. In 2011, BitDefender, Comodo, and others join cloud pioneers McAfee, Norton, Panda, and Trend Micro.

For detection and removal of "zoo malware" (a collection of known worms, bots, backdoors, and downloaders) using traditional methods built into the program, Panda had near-perfect scores in our tests, followed by Avira and G-Data.