Using security software is more important than ever. Our tests of the latest all-in-one security suites show that good protection can shut down the nastiest viruses, spyware and adware.

In the early days of computer viruses, you could get by with careful surfing -- and without antivirus protection. Now, crooks love nothing more than to discover a nasty zero-day security flaw for which there's no defense, and then to infiltrate otherwise benign and popular Web sites with hidden, malicious programming made to attack that security flaw. While relatively uncommon, such tactics can catch even the most careful surfer. Like it or not, you need security tools.

To help you select the best security for your computer, PC World put nine comprehensive suites -- from Avira, BitDefender, F-Secure, Kaspersky, McAfee, Panda, Symantec, Trend Micro and Webroot -- through the wringer. We poked and prodded, surfed and scanned until one contender came out on top.

Our all-around winner this year was Norton Internet Security 2009. Once again Symantec's suite did a fine job combining strong performance with smooth design, starting with a top-tier overall malware detection rate just shy of 99 percent. It sports an attractive and well-laid-out interface, and useful new features in this year's version include "pulse" automatic updates, which send new malware-detection signatures out to your PC every five to 15 minutes.

Symantec also incorporated cloud computing into the suite this year, with on-the-spot online checks to supplement scans that used to occur entirely on your machine. The Norton Insight feature, which compares a new program on your PC against a reputation database of programs that other Norton users have, is meant primarily to improve the suite's performance by preventing it from scanning known safe applications.

Harnessing the immediacy of the Internet is a trend this year. The F-Secure, McAfee and Panda packages all now use similar online checks to attempt to detect new malware more quickly, without having to wait for a scheduled signature update; the approach has the potential to boost overall detection rates.

With new features, strong performance and pleasing design, Norton Internet Security deserves its top spot -- but that doesn't mean it's for everyone. Norton can't perform backups, for instance, while four other suites in this group offer the feature. Also, though Norton's detection rate is very good, it isn't the best: Avira's Premium Security Suite took top honors again this year in identifying both known and unknown malware. What's more, you'll have to pay for the best. At Rs 3500 for three PCs, Norton was the second-most-costly suite we tested; only Kaspersky Internet Security 2009 cost more, at Rs 4000 for three users.

If you want the best all-around security, buy the Norton suite. But for particular needs, you might have better choices -- the less-expensive BitDefender (our No. 2 pick), say, or maybe Avira, the top virus detector (with backups) -- so be sure to read all our reviews before you commit.

How we tested the suites

To evaluate the suites, PC World once again partnered with AV-Test.org. This German organization pitted each suite against its "zoo" of 654,914 backdoor programs, bots, worms, Trojan horses and password stealers, as well as against 46,246 adware samples. Each suite was allowed to connect to the Internet to use online checks, where available.

The group's rootkit tests looked at each package's ability to detect and clean up both active and inactive rootkits -- stealth malware designed to hide criminal software on your PC. AV-Test also assessed scan speed and each suite's ability to clean up a malware infection, and the group's heuristic and behavioral detection tests determined how well a suite could identify new and unknown malware for which it didn't yet have a signature. The heuristic tests used two- and four-week-old signature files with each suite to simulate encounters with unknown malware, while the in-depth behavior tests examined how well each suite could identify malware based solely on how it acted on a PC.

After AV-Test evaluated and scrutinized each suite's innards, we tested its interface and design. We determined whether it smoothly handled alert pop-ups or phishing-site blocks, or whether its actions left us scratching our heads. We combed through all the settings to see whether they were at appropriate defaults, and also whether advanced users could easily change them.

Where security applications are concerned, however, performance and effectiveness outweigh design, so the bulk of our scoring depended on how well a suite detected and disinfected malware, along with how fast it scanned. We also considered price, support and features in the final rankings.