KeyPlusPlus is a spy software that is used to monitor all activity of the computer. It traces every your key press, in fact it sees everything that you do during the sesion. KeyPlusPlus is invisible keylogger, which gives you possibility to see what saw the user. This software is very usefull to trace childrien or workers when they are using the computer when you cannot look after. Although this might be legitimate purpose in some settings, this is a privacy risk in most cases.

Source: http://www.2-viruses.com/remove-keyplusplus