What to look for if you think your cell phone is being tapped
Pay attention to the temperature of the battery.
If your cell phone battery gets unusually hot when not in use and you can think of no reason for it to do so, there might be tap software running in the background and causing your phone's battery to be in constant use. Of course, a hot battery could just be a sign that it has been overused. This is especially true if your cell phone is already older than one year, since cell batteries tend to decline over time.
Note how frequently you need to charge your phone.
If the battery life of your phone suddenly drops without reason, prompting you to charge it twice as often, the battery might be dying because of tap software constantly running in the background and eating up power. You also need to consider how often you have been using your phone. If you have used it a lot lately, the increased need for a good charge is probably just due to the fact that you have used more of its power. This is only applicable if you barely touch your phone or have not used it any more than normal. You can monitor the life of your smart phone's battery over time by using an app like BatteryLife LX or Battery LED. Also note that a cell battery will lose the ability to stay charged as it gets older. If this change happens after you have had your phone for a year or more, it could just be the result of an old, overused battery.
Try shutting down your phone.
If the shutdown process gets delayed or cannot be completed, this strange behavior could indicate that there is someone else controlling your phone through a tap. Pay close attention to determine if your cell phone takes longer to shut down than usual or if the back light remains on even after you shut it down. While this could be a sign that your cell phone is tapped, it could also just mean that there was a glitch in the hardware or software of your phone that is completely unrelated to a tap.
Watch for random activity.
If your phone lights up, shuts down, starts up, or begins to install an app without you doing anything, there might be someone hacking into your phone and controlling it through a tap. On the other hand, any of this could happen if there is random interference during the transmission of data.
Note unusual text messages.
If you have recently gotten SMS text messages that consist of randomized strings of letters or numbers from unknown senders, these messages are a major red flag that there is an amateur tap on your phone. Some programs use SMS texts to send commands to the target cell phone. If these programs are installed sloppily, these messages can appear.
Pay careful attention to your phone bill.
If the cost of your data jumps up and you know you are not responsible for the increase, there might be someone else using your data through a tap. Many spy programs send logs of your phone records to online servers and use your data plan to do so. Older programs used large amounts of data, making them easier to spot, but newer programs are easier to hide because they use less data.