The Google AdSense blog announced they are taking both automated and manual actions against publishers that use clickjacking techniques to trick users to click on ads. Basically, an ad might be placed in a location that a user thinks is real content, but the ad is hidden there so that when you click on the content, the ad click is triggered. This is also known as UI redress.
Here is an example GIF Google made to explain it:
Google said earlier in the year they had manually terminate accounts of those publishers doing this but also worked on automated methods of spotting these efforts. Google said their "engineering team worked in parallel to quickly release a filter to automatically exclude this type of invalid traffic across display ads."
"This approach delivered a one-two punch to publishers who violated our policies: our operations team, which forms an early line of defense against invalid traffic, cleaned out publishers from our ad systems, while engineers built a new filter as a durable defense to protect against Clickjacking traffic," said Google.
Forum discussion at Google+.