Conor Brophy: Although a question mark hangs over its cost, ad fraud is far-reaching

And with advertisers increasingly spending money in mobile, fraudsters are on the move

Internet advertising fraud is a big problem. Just don’t ask how big.

Estimates vary wildly. Two reports published in recent weeks arrive at estimates as far apart as $7.2 billion and $12.5 billion on the money lost due to ad fraud in 2016. The first, by the US Association of National Advertisers and White Ops, predicts that will fall to $6.5 billion this year. The second, by Adloox, expects the cost of fraud ...