Functionality-Usability-Security Model simply shows that you can't focus on all the three of them at once in a software or system. If you focus on either of the security, functionality and usability one will always have to suffer, an example of this is the ATM machines where the functionalities are limited and its not very user friendly since the focus is(should be) on Security. A fact that we IT's must consider is that the more advanced the technology is the more exploitable it becomes. A perfect balance in the FUS model might be just a theory. However, the way I see it nothing is ever really secured, there is always a loophole in the system. It's just up to you on how many layers of security you want the attackers to go through before reaching the information he needs. Exploits are made to test the integrity of the system, however, when given in the wrong hands results may be deadly. People nowadays use these smart-phones, smart-watch, smart-tv...etc which all...