Free security suites have long been offering protection for Windows computers that has ranged from adequate to excellent. After using the Avast 6 beta for the past week, it looks like Avast 6 will land far closer to the high end of the spectrum thanks to its new WebRep browser add-on and sandbox environment, unique in the free antivirus marketplace.

Avast 6 Free will come with a sandbox feature to isolate risky programs while they run.

The security suite is available in three forms: Free Antivirus, which replicates the features available in the upcoming Avast 6 Free' Pro Antivirus, which offers a 30-day trial for checking out Avast's first level of paid security' and Internet Security, which ramps up the feature set to include more security tools.

The biggest new feature is the AutoSandbox, which walls off suspicious programs, preventing them from potentially damaging your system while allowing them to run. Few details have been provided so far as to how the AutoSandbox works, however a response from an Avast employee on Avast's forums gave some indication of how it works. Avast's sandbox allows the program to run, while keeping track of which files are opened, created, or renamed, and what it reads and writes from the Registry. These permanent changes are virtualized, so when the process terminates itself, the system changes it made will evaporate.

The AutoSandbox settings are accessible from the new Additional Protection option on the left nav. It defaults to asking the user whether a program should be sandboxed, although you can set it to automatically decide. There's a whitelist option for programs that you always want to exclude from the sandbox, and you can deactivate the feature entirely.

Avast 6 will come with an optional browser plug-in for Internet Explorer and Firefox called WebRep, which is Avast's new Web site reputation service. It uses a combination of data from Avast's virus labs and user voting to determine a safety score for a site. Similar add-ons are a common tool available in most antivirus suites, so it's good to see Avast join them. Like its competitors, Avast appears to have ignored Google Chrome and its 10 percent market share when it comes to search result rating add-ons. However, Avast has promised that the Chrome add-on will be released soon.

The browser add-ons install when installing Avast 6. If you don't want them, it's actually easier to remove them from within Avast instead of within the browser. Currently, removing the add-on using the browser's interface will cue Avast to re-install the add-on the next time the computer is rebooted.

Other new features have been introduced in Avast 6 beta. The Troubleshooting section now comes with a "restore factory settings" option, there's a new sidebar gadget for Windows 7 and Vista, and you can set automatic actions in the boot-time scan. Two features that have filtered down to the free version are the Script Shield and site blocking. The Script Shield now works with Internet Explorer 8 and 9's protected mode. Meanwhile, the paid versions have gained some new features, such as SafeZone, a virtualization feature for secure online banking. The installer has shrunk for all versions by about 20 percent.

Avast 6 Free also comes with the optional WebRep add-on, for rating search results and Web sites.

The initial build of the program was buggy and actually caused my computer to enter into a crash loop that I escaped by booting into Safe Mode and removing it. However, subsequent builds have proven to be far more stable. Note that if you do install the beta, you'll have to completely uninstall your current antivirus program, even if it's Avast 5. The company expects to have an upgrade mechanism in place by the time Avast 6 is ready for wide distribution.

Other known problems in the beta include the fact that the SafeZone feature doesn't work yet and that the firewall in the paid versions contains a conflict with uTorrent.

Performance benchmarks are not available because of the in-development nature of this release. It's simply changing too quickly for benchmarks to provide any useful information, given the time it takes to conduct them.

Although the suite looks good and bodes well for the coming public release, this is a beta product and so it's not recommended for security duties on your primary or only computer. However, it's well worth exploring on secondary machines, and it's encouraging to see Avast not laying fallow after the gains made in version 5.

The beta announcement thread on the Avast forums can be read here.