To evaluate our approach, we reconstructed the SMS sniffing Tro jan scenario. We implemented a simple SMS sniffing Tro jan by registering for android.pro- vider.Telephony.SMS RECEIVED events. This is the way SMS messages are received by any application, including malware [27]. Our Tro jan grabs SMS messages as soon as they arrive and pops up a message box to show ”SMS inter- cepted” as well as the message text, thus providing immediate feedback when the message has been intercepted. In a second step, we implemented the OtpMes- sages application. The application registers to receive incoming SMS messages using the same method as our Tro jan. Every time OtpMessages receives an SMS message, it will display a pop-up containing the message and the string ”OTP Message Received”. This way, we can easily distinguish between our two appli- cations. For the actual evaluation we crafted a number of SMS messages that contain OTPs. We sent the crafted messages from another mobile phone to our test device. All messages that contained any of the keywords were only received by the OtpMessages application. To verify that our Tro jan still works, we sent a few messages to the phone that do not contain the filter string. Those messages were received by the Tro jan.