Whoops! That's what Yahoo is saying, or at least should be saying, after it was discovered that some of their banner ads have been serving up malware. While nobody would assume that Yahoo would endorse peddling nasty software to people’s machines, the article asserts that the technical teams at Yahoo might not even be aware that there is a problem. It seems that certain banner ads are hosted on or are contacting servers that produce pop-ups eerily similar to Windows dialogs. We've all seen them before, but most of us are wise enough to know that Windows dialogs urging you to fix a problem now (and possibly pay for it) are bad news.
Unfortunately for Yahoo, and just about any company that relies on ad revenue, the multitude of ad-serving companies in existence makes it hard to track each and every individual ad. Hopefully they will track down the culprits involved regardless, before too many users find themselves with spyware.