Sometimes it could even be symptomatic of malware. The good news is that Opera has recently updated its Opera Max app with a new feature in the form of notifications. The app will now be able to let users know when an app uses data in the background, and will also tell you exactly how much data is being used.
For those of you with limited data, this will be a good way of keeping track of the amount of data you use to prevent yourself from going over, and also a good way to checking which apps are the data hogs (and potentially battery hogs since constantly using data will drain your battery). The app has a set limit of 10MB, meaning that if the app uses more than that in a week while in the background, it will notify you.
Users will then have the ability to block the app from doing so. If you have yet to download Opera max, then head on over to the Google Play Store and check it out.