Android malware developers are stepping up their billing fraud game with apps that disable Wi-Fi connections, surreptitiously subscribe users to pricey wireless services, and intercept text messages, all in a bid to collect hefty fees from unsuspecting users, Microsoft said on Friday.
This threat class has been a fact of life on the Android platform for years, as exemplified by a family of malware known as Joker, which has infected millions of phones since 2016. Despite awareness of the problem, little attention has been paid to the techniques that such “toll fraud” malware uses. Enter Microsoft, which has published a technical deep dive on the issue.
The billing mechanism abused in this type of fraud is WAP, short for wireless application protocol, which provides a means of accessing information over a mobile network. Mobile phone users can subscribe to such services by visiting a service provider’s web page while their devices are connected to cellular service, then clicking a button. In some cases, the carrier will respond by texting a one-time password (OTP) to the phone and requiring the user to send it back in order to verify the subscription request. The process looks like this: