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Im wondering if you have any issues with your touchscreen. Sometimes the digitizer can come unseated slightly and can cause the same issue with random letters being typed. It looks like a ghost is doing it, but it's just that the screen is uneven and thus there is pressure added to a certain part of the screen causing letters to be typed (often the exact same letters.) So, I'd make sure either way, as to what the problem actually is.
Did reset didn't work. The lock ring would start bouncing toward message icon then go to where you start new email and start putting i'm user name, the farthest I let it go is when the password started then pulled battery.
I would do a factory reset, and change all your passwords. Also be sure to read the permissions when installing a new app.
Is it a yahoo email account that you see being hacked?
Android Botnet Seen Spewing Spam - Security - Mobile Security - Informationweek

I have seen the person type on it
It's a freaking digitizer people. You're looking for zebras when you should be looking for horses.