9 Protection and Operating-System Design Free Online FlashCards

How do protection and security differ?

Protection mechanisms restrict access to resources; security is the broader goal of preventing unauthorized access, misuse, or damage.

What should a secure default do when permission is unspecified?

When permission has not been explicitly granted, access should generally be denied.

What are subjects, objects, and rights in a protection system?

A subject is an active requester, an object is a resource, and rights specify which operations the subject may perform on that object.

What does authentication establish?

Authentication establishes or verifies an identity.

How does a process’s virtual address space support isolation?

A process typically has its own virtual address space; hardware and the operating system translate its addresses and prevent direct access to other processes’ or kernel memory.

How do system calls provide a controlled boundary?

A program requests a service through a system call; the kernel checks and performs the privileged operation instead of giving the program unrestricted hardware access.

How does the operating system mediate access to files and devices?

File permissions and other access controls regulate file operations, while processes access devices through operating-system interfaces rather than controlling hardware directly.

How can CPU scheduling support availability?

Scheduling allocates CPU opportunities, and avoiding indefinite resource monopolization helps support system availability.

What do locks help prevent in concurrent systems?

Synchronization mechanisms such as locks help prevent conflicting concurrent operations; shared resources must also be protected from unauthorized access.

Why must operating-system protection use multiple layers?

No single mechanism is sufficient: for example, memory isolation cannot correct inappropriate file permissions, and file permissions cannot prevent a faulty kernel component from corrupting memory.

What does authorization determine?

Authorization determines which operations an identity, or a process acting for it, is permitted to perform.

What is the purpose of access enforcement?

Access enforcement ensures requests cannot bypass the authorization decision.