Understanding protection rings
Before we explain vulnerabilities that can be exploited because of permission problems, it is important to understand the concept of protection rings in operating systems.
The term protection ring refers to a hierarchical mechanism implemented on CPUs and utilized by operating systems such as Windows to protect the system by providing fault tolerance and, of course, to better protect from malicious activity and behavior. Each ring in this mechanism has a unique role in the overall functioning of the operating system, as seen in the following illustration:
The lower the number of the ring, the closer it is to the hardware and, therefore, the higher its privilege level. As you can see in the illustration, Ring 0 is the operating system kernel, which provides "back-to-back" access to the hardware from the higher rings and vice versa. Antivirus software tends to deploy its inspection...