Symantec is set to introduce a new tool to help them avoid unpatched software flaws.

The Symantec Online Network for Advanced Response (SONAR), will look at the behaviour of programs running on the computer in order to decide whether they are malicious. This is a departure from Symantec's traditional signature-based anti-virus protection techniques, which compare the program's code to a database of known malware.

SONAR will be a free add-on to Symantec's Norton AntiVirus 2007 and Norton Internet Security 2007 products, said Ed Kim, director of product management with Symantec's consumer business unit.

"We're very excited about the release of SONAR," Kim said. "It's zero-day protection that doesn't rely on threat signatures."

Zero-day attacks are based on flaws that are unknown, or have not yet been patched by the vendor, and they are particularly effective against signature-based anti-virus protection. SONAR uses an algorithm to evaluate hundreds of attributes relating to software that is running on the computer, so it can spot malicious software, whether it's already been identified by Symantec researchers or not.

SONAR makes its determination based on whether the software does things such as add a shortcut on the desktop or insert itself into the Windows Add/Remove programs list, both of which indicate it probably isn't malware, Kim said.

The software is built on technology that the company acquired after Symantec's purchase of WholeSecurity.

Symantec already sells a similar behaviour-based security product to enterprise users, called Critical System Protection, but with SONAR, Symantec is finally saying that its behaviour-based techniques are ready for the consumer desktop market, said Andrew Jaquith, senior analyst with Yankee Group Research.

The software comes not a moment too soon, he added. "Signature-based technologies for viruses and spyware certainly work, but their coverage is increasingly thin. So you need to bolster signature-based approaches with behaviour-based approaches."

Symantec is also launching new versions of its consumer software that will run on Microsoft's upcoming Vista operating system. The company is shipping versions of Norton Internet Security and Norton Antivirus that are Vista-ready, with other products to follow in the next months.

The Vista version of Norton Confidential will ship in early February, and Norton Save & Restore will be Vista-ready some time after the operating system's late-January consumer launch, Kim said.

Symantec's Norton 360 will support Vista when the next-generation consumer protection service ships. That is expected to happen in late February or early March, Kim said.