Malvertising is insidious, and can be delivered on a wide scale simply by displaying an advertisements on a web page. It’s usually spread without the knowledge of the site hosting the ads, and without the knowledge of the ad network the malware is riding on. That means that an email to the blog owner that “your ads infected my computer with a virus” will be inevitably met with confusion. Emails from site owners to their advertising partners will get a similar response. And it’s becoming much more common.