I noticed a message to a number I don't know

[Android Central Question]

Hello all!. Some background I received a text from a number that said something along the lines of "Hello [my name], I have good news. Call me when you can." I didn't recognize the number and did some googling and determined this was spam and ignored it. Then a day later I go to text someone and I see a text i didn't write to a number I didn't know and that was essentially "<[random letters and numbers>" I have since factory reset my phones and changed a bulk of my passwords but I am still dumbfounded how this might have happened, any thoughts?

 

[B. Diddy]

Welcome to Android Central! One of the more common things malware does is to send SMS to numbers that might cost you money (e.g., premium SMS messages). It's possible that some app you installed was malware in disguise, or malware got onto the phone some other way. A factory reset will usually do the trick, but be cautious about reinstalling all of your previous apps. See if the odd sent texts persist -- if they do, then the malware might still be on the phone. Some malware will install to the system root, which makes it difficult to get rid of. You usually have to reinstall the firmware completely in those situations.