The Norton security software included at no extra charge with Comcast's Internet service is only for Windows and Mac desktop and laptop computers. For mobile devices (phones and tablets) they offer "Norton Mobile Security" for $20/yr. See http://constantguard.comcast.net/products-and-services/. Norton itself presently has a special on that product for $15, see https://us.norton.com/norton-mobile-security.
The Play store has many security apps available, some of which are free.