P1L3: Operating Systems Flashcards
What does an Operating System do? What does it provide?
- -Makes it easier to use resources
- -Hardware controlled by OS
- -Provides isolation
What is a Trusted Computing Base (TCB)?
–OS has direct control of hardware resources
–OS must determine authorized user(s) of resources
What are TCB Requirements?
- Complete Mediation–OS is between HW resources and apps
- OS must be tamper-proof
- OS must be correct–Protected resources are used properly.
OS and Resource Protection
–Establish the source of the request (ie authentication)
–Authorization or Access Control
–OS follows policies for authorization and authentication
What are System calls?
A request to the operating system.
What is Complete Mediation?
Ensures that the OS cannot be bypassed when accessing a protected resource
What are the requirements for isolation?
–requires HW support for memory protection
–The processor must keep track of what kind of code is being executed
–Privileged instructions can only be executed in system mode
Are system calls more expensive than regular function calls? If so, why?
Yes. Because of the info that must be saved, the memory mapping that must be done, and the special instructions.
What is Memory Protection?
The HW determines if memory belongs to the OS and is therefore unwritable to users.
How do processes achieve unit isolation?
Each process gets an address space for it to use
What are Physical addresses?
Point to actual RAM or physical memory
What are Logical addresses?
Point to the address space
What is Address translation?
The translation between the logical and physical memory.
Logical addresses are stored on ____
pages
Physical addresses are stored on _____
frames
What is a Page table?
Table used to translate between pages and frames. It is built and protected by the OS
Performing regular backups of data on a system is a critical control that assists with maintaining the integrity of the system and user data. T/F
True
The default configuration for many operating systems usually maximizes security. T/F
False
Each layer of code needs appropriate hardening measure in place to provide appropriate security services. T/F
True
A malicious driver can potentially bypass many security controls to install malware. T/F
True
It is possible for a system to be compromised during the installation process. T/F
True
_____ applications is a control that limits the programs that can execute on the system to just those in the explicit list.
White-listing
The most important changes needed to improve system security are to _____.
- disable remotely accessible services that are not required
- ensure that applications and services that are needed are appropriately configured
- disable services and applications that are not required
Security concerns that result from the use of virtualized systems include:
- Guest OS violation.
- Guest OS monitoring by the hypervisor.
- Virtualized environment security.
Once the system is appropriately built, secured and deployed, the process of maintaining security is _____.
Continuous
The first critical step in securing a system is to secure the _____.
Base Operating System
The first step in deploying new systems is _____.
Planning
Planning
Which of the following need to be taken into consideration during the system security planning process
- how users are authenticated
- the categories of users of the system
- what access the system has to information stored on other hosts
Guest OSes are managed by a ________ , or VMM, that coordinates access between each of the guests and the actual physical hardware resources.
Hypervisor, virtual machine monitor
_______-is a reactive control that can only inform you about bad things that have already happened.
Logging
The three operating system security layers are: physical hardware, operating system kernel and _________
User Applications and Utilities
__________ refers to a technology that provides an abstraction of the computing resources that run in a simulated environment.
Virtualization
The final step in the process of initially securing the base operating system is_________
security testing
What does Hardening mean?
to make more secure
What are the Requirements of a TCB (trusted computing base)
Isolation (tamper proof), Complete mediation, verifiable (correct)
Call Gates
System calls used to transfer control between user and system
Memory Management Unit (MMU)
Uses page tables to resolve virtual addresses to physical addresses
User code cannot access physical resources. T/F
True, only system mode’s privileged instructions can
What are Virtualization’s 4 security layers?
Physical hardware, Hypervisor/VMM, Guest Os Kernel, User Apps
