Qualys is inviting sys admins to sign up to a new free service, QualysGuard Malware Detection, which provides alerts about drive-by-download attacks and malicious scripts on monitored websites.

The service is based on behaviour analysis and offers automated alerts when it finds websites with rogue JavaScript, character encoding inside inline frames or malware. These alerts will identify the location of a suspicious file but typically won't name the threat. Qualys' service, launched in beta on Monday, may incorporate naming in future. This would most easily be delivered via a partnership with an anti-virus firm.

QualysGuard Malware Detection crawls monitored websites daily through a bank of virtual machines running unpatched copies of IE6 and Windows to see if anything iffy occurs. McAfee SiteMonitor and services bundled with Google and Yahoo provide surfers with site scans that are sometimes incorrect.

Chief technology officer at Qualys Wolfgang Kandek said its service would provide evidence for sys admins in challenging false positives. He described results from other malware scanning services as "uneven". Tainted ads are often a source of malware. Kandek said Qualys' service would detect if sites were serving rogue third party ads but it may not help much in pinning down which ad is at fault, a practical difficulty in several real cases we've come across in recent weeks.

Sys admins are invited to sign up for QualysGuard Malware Detection here.

Qualys is best known for its widely-used on-demand vulnerability scanning service. The malware detection service is a expansion into a adjacent area of net security and an opportunity to up-sell its new QualysGo Secure. This is a paid-for service that allows companies to check whether they are being proactive in fighting malware and other security threats on their sites and that their SSL cert is in order. Qualys Go Secure subscriptions cost a pricey $995 per web site per year. Successfully passing the Qualys audit allows firms to display a "Secure Seal".

The service is broadly similar to VeriSign's Trust Seal, which costs a more modest $299 a year, but includes SSL cert verification and a scan for web application vulns such as SQL injection bugs advent from the VeriSign service. ®