A new Google service will alert corporate and public users if they are about to visit a site that might contain malware.

Users clicking on such links will be diverted to a warning page, and in future Google intends to provide more information about the nature of potential threats.

The search giant is using data collected by the StopBadware.org project set up by Harvard and Oxford Universities. The service is similar in concept to the Scandoo system from ScanSafe and SiteAdvisor from McAfee.

Eldar Tuvey, chief executive of ScanSafe, welcomed Google's efforts to make web surfing safer but warned that relying solely on a database of dangerous URLs identified by StopBadware would not completely remove the risk of visiting a malicious site.

"Benign web sites can be subverted to host malware for short periods of time in order to avoid detection," Tuvey said. " Real-time scanning is most critical when a site hosts malicious 'drive-by' malware code like this."

McAfee security analyst Greg Day added that the service failed to mitigate the risks of visting a site which appears normal but tries to sign users up to spam or links through to malicious sites.

Tom Newton, product manager at network security vendor SmoothWall, said that this latest “Neighbourhood Watch” scheme is another advance for StopBadware, but warned that the coalition will have to be careful in defining what constitutes a dangerous site.

"The questions arise – how do they define badware, and is badware always bad? " Newton asked. "The coalition and Google need to be careful when categorising technologies so that they are not unfairly demonising web sites which may be performing perfectly legitimate practices.”