Long the scapegoat of all manner of society’s ills, porn is no longer the source of the largest number of malware problems on mobile, according to security firm Bluecoat.

Web ads are now to blame for 20 per cent of mobile malware visits, according to Bluecoats analysis of more than 75m smartphone users, growing from just 5.7 per cent in November 2012. Pornography was the biggest driver of malware visits two years ago, at 22 per cent, with web ads coming in fourth, but has dropped to a 17 per cent share.

The growth in the mobile advertising industry has boosted the development of rogue ads, or malvertising, the report said. Delivered by the same means, it is difficult for browsers to tell the difference. Many ads today, legitimate or not, are also clicked on by mistake.

The report highlights that many malware threats targeting mobile devices are still pretty basic, largely confined to bad apps and SMS scams. In-app ad threats can leave smartphone users open to having personal information intercepted, like detailed usage habits, telephone number, SIM unique IMEI code and contacts.

“The lack of clear requirements for developers to explicit identify what data their apps access, log, store and share, which makes it difficult for users to make risk-based decisions about how they use,” the report said.