Eavesdropping on a computer user's keyboard input is called keylogging...
Keylogging is much harder to pull off on smartphones because most mobile operating systems allow only whatever app is on screen to access what you are typing, says security researcher Hao Chen of the University of California, Davis.
However, Chen and his colleague Liang Cai have got around that hurdle and created a keylogger that runs on Android smartphones. It uses the phone's motion sensors to detect vibrations from tapping the screen. Since mobile operating systems do not treat the motion-sensor output as private or in need of protection, it presents a target for hackers wanting to create an innocent-looking app that secretly monitors phone users. (more)
