Millions exposed to malvertising that hid attack code in banner pixels

The malicious script is concealed in the alpha channel that defines the transparency of pixels, making it extremely difficult for even sharp-eyed ad networks to detect. After verifying that the targeted browser isn't running in a virtual machine or connected to other types of security software often used to detect attacks, the script redirects the browser to a site that hosts three exploits for now-patched Adobe Flash vulnerabilities.

Despite targeting only people using IE and unpatched versions of Flash, Stegano is noteworthy for its concealment of exploit code in the pixels of the banner ads. There's no reason future campaigns—or possibly ongoing ones that have yet to be discovered—couldn't exploit zero-day vulnerabilities that infected a much larger base of people. Until ad networks get much better at detecting malvertising campaigns, the scourge is likely to continue.