Malwarebytes is a security firm which has warned people who download rogue apps that they can expect to fall into an insecurity trap and will be very dangerous to their Android firmware upon time.
Malwarebytes has also said that the SMS Trojans are some of the most prevalent malicious apps and warned that some can charge people as much as $10 for every crappy message that they send or receive.
Jerome Segura ( Senior Security Researcher at Malwarebytes ) has traced certain issues and stated as per source ;
We navigate to a site pushing a fake Skype update for Android smartphones and tablets. We proceed to download the app which is fairly big in size, but is within what we would expect for Skype anyway.The code is well-structured and each class is named appropriately, quite different when we compare it to malicious Java applets used in exploit kits where everything is obfuscated and encrypted. What we have here is the backbone for an SMS Trojan that can automatically send costly (Premium) SMS messages while running silently in the background. The Android operating system comes with certain safeguards and given the current malware landscape it is a very good idea to make sure they are enabled. The rule of thumb is that you should avoid installing any app that is not in the Google Play Store. Right there it will dramatically reduce your chances of getting infected.