The online ad industry is rallying to fight piracy, fraud, extremists and fake news. Does it stand a chance?

Media companies and their advertisers are shortchanged $8 billion a year because of scams, or more than the estimated combined revenue of Lionsgate, Paramount Pictures and MGM Studios. Advertisers think they're getting the desired views and clicks. But companies taking closer looks are finding unwelcome results. Websites where ads appear are visited by robots — computers hacked to impersonate real browsing behaviors. Others traffic in content people crave but upstanding businesses wouldn’t want to support, such as bootlegged movies or terrorist propaganda.

The set-up is siphoning potential revenue from legitimate media companies to shady ones. And it’s enabling hucksters to profit in fake newswriting and piracy thanks to ad views. Stopping money from flowing to their operations has become a new priority for advertisers. Their results are difficult to measure, but early signs are encouraging.