I received a SMS text message from a number I don't recognize. It had a file with it, but when I opened it there was nothing there all it said was "B". I get files all the time because of work. But I want to find out if this file has something hidden in it, like hacker or tracer stuff, etc. Because B is my first initial. How can I determine that? Can I send the file to avast to have them check it, if so how do I do that? Thanks