Researchers at Microsoft are looking at a virtual machine “Rozzle” to detect browser malware that remains hidden until it finds the right plug-in or browser flaw to exploit.
Rozzle, an extension of the researchers' previous work on web-hosted JavaScript threats, was an attempt to deal with the increasing number of JavaScript malware attacks that exploit browser and plugin vulnerabilities.
Although most malware today remained "naive" about detection avoidance, the researchers feared more sophisticated techniques such as browser "fingerprinting" [PDF] could undermine existing defences.
“Using current fingerprinting techniques, just about any piece of existing malware may be made virtually undetectable with the current generation of malware scanners,” the researchers noted.
Browser fingerprinting allows the attacker to automatically select the most appropriate exploits depending on the browser make and associated software plugins.
For example, one piece of malicious JavaScript code they found built a profile of the browser and recorded the presence of Adobe Acrobat, Quicktime, Java plugins, and Windows Media Player. After taking the fingerprint it was instructed to fetch the malware that best fit the profile.
Besides enabling more efficient targeting, the style of attack posed a second problem for malware detection since it only became visible in the right environment.
Rozzle would deal with this game of hide and seek by running “multiple execution paths in parallel”.
Using 65,855 samples of JavaScript malware, a standard runtime malware detector picked up just 2.5 per cent of the sample, while with Rozzle activated on a browser, it detected 17.5 per cent, the researchers claimed.