The automation of the advertising industry was supposed to reduce waste. But in a quest for greater efficiency, marketers have exposed themselves to a new challenge: fraud.

The uncomfortable truth about the $120bn digital advertising market is that the fastest-growing and most innovative part of the sector – open exchanges – is increasingly being exploited by criminals.

With concern among its clients mounting, WPP, the world’s biggest ad agency, last month said it would stop buying ad slots through such exchanges. These technology platforms, operated by Google, Facebook, AOL and Yahoo, allow marketers to place ads on hundreds of thousands of sites across the internet. But in doing so they have left the industry vulnerable to fraudsters.

Many worry that if unchecked, fraud will undermine confidence in digital advertising. That could hinder the industry’s efforts to capture the $400bn that brands spend on traditional media advertising such as television and newspapers.http://www.ft.com/intl/cms/s/0/85492590-0801-11e4-9afc-00144feab7de.html#axzz39101cYZe