Opera Software will include anti-malware and drive-by download defenses in version 9.5 of its flagship browser, which is now in beta but close to a final release, the company said Monday.

Part of Opera's "Fraud Protection," which until now has included only anti-phishing tools, the new feature puts up messages that warn users when they're about to visit a site that's a known malware host or has been hacked to serve up Trojan horses, worms and other malicious code. The list of blackballed sites is provided by HauteSecure, said Thomas Ford, an Opera spokesman.

"It's significantly different than Firefox's [anti-malware protection] in a couple of key areas," Ford said. The Haute Secure-delivered list, he said, drills down to the page level and also integrates user-provided information on hacked sites. "Haute Secure also uses a community as a human verification layer," Ford said. "It's a false-positive remediation."

HauteSecure already provides a free toolbar for users of Microsoft's Internet Explorer and Mozilla's Firefox browsers.

The browser queries the Norwegian company's servers each time a page is requested, Ford said, and retrieves a HauteSecure-created blacklist for any compromised pages in that domain. "The data rarely exceeds 1K," said Ford, "so it's not a performance problem, even for low-bandwidth users, like those on dial-up or mobile users."

By comparison, Firefox's anti-malware tool downloads an updated blacklist generated by Google -- and provided via Stopbadware.org, a group that Google co-founded -- daily, then stores that list locally.

"We don't store the blacklist in the browser itself," Ford said. Instead, Opera's Fraud Protection architecture lets the company pull in security information from any external provider. "We can take any data source," Ford added.

All desktop versions of Opera 9.5 -- for Windows, Mac OS X and Linux -- include the anti-malware protection, but Ford wouldn't confirm that the tool would be rolled into Opera's mobile browser, prominent on smart phones such as those made by Nokia Corp. "All I can say is that [the feature] is in the core of the browser."

The newest beta, which can be downloaded from the Opera site, includes the new anti-malware feature. Opera has not committed to a release date for version 9.5, although Ford said it was "imminent."