How does the distinction between monitor mode and user mode

How does the distinction between monitor mode and user mode function as a rudimentary
                                form of protection (security) system?

Solution

The distinction between kernel mode and user mode provides a rudimentary form of protection in the following manner. Certain instructions could be executed only when the CPU is in kernel mode. Similarly, hardware devices could be accessed only when the program is executing in kernel mode. Control over when interrupts could be enabled or disabled is also possible only when the CPU is in kerne l mode. Consequently, the CPU has very limited capability when executing in user mode, thereby enforcing protection of critical resources