These are apps in mobile devices that trick users into downloading them by using legitimate companies or popular references. They may also pose as attractive apps, providing interesting services like live wallpapers or real-time spying tools.
File infecting viruses, or file infectors, generally copy their code onto executable programs such as .COM and .EXE files. Most file infectors simply replicate and spread, but some inadvertently damage host programs.
A firewall prevents computers on a network from communicating directly with external computer systems. It acts as a barrier through which all information passing between the networks and the external systems must travel.