At least one in 10 web pages are booby-trapped with malware, according to Google.

A five-strong Google research team found that 450,000 pages, out of a sample of 4.5 million pages, contained scripts to install malicious code, such as Trojans and spyware on vulnerable PCs, the BBC reports. This is a conservative estimate - another 700,000 pages given the once-over were thought to be suspicious by Google.

Google's Ghost in the Browser study (PDF) covers the well-understood problem of drive-by-downloads from compromised sites, which are eclipsing virus-infected email as a means to spread malware. The study takes the debate further chiefly by presenting evidence about the sheer volume of web content on the "dark side" of the net. As well as hacker-run websites, malware can be injected into otherwise legitimate site via a variety of ruses, the Google team explains.

The tricks include hacking into a web server to plant malware, or planting it within third-party widgets or advertising. User-generated content also creates a means to upload malware. The researchers hope to use their findings to "map" the problem and aid the development of a new generation of safe surfing tools that steer users away from harm. ®