Many people think that Android is virus free. However this is not the case. There are many viruses to take over your phone and make you pay money to get it back.
However, the problem does have a solution. There are also many anti virus apps on the play store to help you.
One of these apps is Avast Antivirus for Android. A download link is here:
It is full of features to protect your android device and will alert you if your phone or tablet is contaminated with a virus and will protect it when it does not.