Starting today, Internet Explorer’s SmartScreen Filter will begin attempting to identify these ads and warning users about their presence.

What constitutes a deceptive ad?

Ads that attempt to trick users into downloading malicious software are at the top of the list for obvious reasons. So too are ads that try to force a download when clicked.

But Microsoft’s update SmartScreen Filter goes beyond the most dangerous ads. The software giant says it’s also looking for “advertisements that make it difficult to tell whether a user is looking at website or advertisement content.”

As Microsoft’s Michael Johnson and Barak Shein point out, “in many cases these ads are created so that a user doesn’t realize that they are looking at an advertisement.”

A harbinger of bigger problem for publishers?

When the SmartScreen Filter detects an ad that it suspects violates Microsoft’s evaluation criteria, the browser will block a request and warn the user that “The website has been reported as unsafe.” While the user will have the ability to disregard the warning and continue on to the site, it’s likely that many won’t.

That, for obvious reasons, is a problem for publishers. The even bigger problem: many publishers may have little ability to ensure that they’re not caught up in Microsoft’s SmartScreen Filter. 

That’s because so many publishers rely on ad networks and have limited knowledge of all the ads that may be running on their sites at any given time.

Even legitimate ad networks that don’t knowingly serve up the kinds of ads Microsoft is targeting have proven vulnerable, so publishers shouldn’t assume that their ads will always be clean just because they’re working with reputable ad partners.

So what should publishers do?

Most probably don’t need to panic. Deceptive ads, while prevalent, aren’t everywhere. And Internet Explorer’s market share isn’t what it used to be. But Microsoft’s more aggressive stance should serve as a reminder to publisher that digital ads are under attack on multiple fronts even they remains one of the most lucrative ways to monetize an online business.