These Android apps carried out their main, advertised functionality – but also sent users ads that take up half a device’s screen as soon as the phone is unlocked.
This is regardless of whether the app is running on an Android device or not.
Igor Golovin, security expert at Kaspersky, said: “Nowadays we heavily rely on our phones.
“We work, share personal information and watch entertainment – all on our mobile devices. Obviously, this attracts adware creators’ attention.
“The problem here is that adware does not create usability inconveniences that frustrate users; it also – with improperly developed SDKs – could result in data leakages.
“As an additional way of monetisation, developers of those SDKs may profit from selling user data relevant for targeting purposes to third parties to customise ads they are showing to users, without their permission.