Operating System Security (PPT 7) Flashcards
What is Security?
It is the collective name given to tools, resources and administrative procedures that are designed to protect computing data and services
What are the four key areas to protect?
Protection
-Access to the data must be controlled
User Authentication
-Access to the computer facility must be controlled
Network Security
-Data must be securely transmitted through networks
File Security
-Sensitive files must be secure
What are the four types of generic computer threat?
Interruption
-System assets become unavailable (e.g. cutting off connection)
Interception
-Unauthorized access to system asset (e.g. hacker copying files)
Modification
-Unauthorized modification to a system asset (e.g. virus changing a program or destroying data)
Fabrication
-Unauthorized faking of an object in the system (e.g. adding records to a file)
What is a virus?
It is a small program that can attach itself to an existing program. When the infected program is run, the virus code is also run. When a virus is run, it can try and replicate itself. If it runs fast enough, the user is unlikely to notice it
What is a Stealth Virus?
It is a virus which attempts to cover itself up. One way is to compress the original file so it still appears to be the same size
What are five security design principles?
- Least privilege
- Small, uniform security
- Acceptability of the security measures
- Complete mediation
- Open design
What is Least Privilege Security?
- processes operate using the smallest number of privileges possible
- default is “no access allowed”
- privileges gained by explicit permission
What is Small, Uniform security?
- small and uniform implies easy to verify their correctness
- part of design, rather than ad-hoc
What is Acceptability of security measures taken?
- shouldn’t get in the way of the user’s work
- if security mechanisms are difficult to use, they might be ignored
What is Complete Mediation?
- every access checked against access rights
- including those during maintenance
What is Open Design?
- the effectiveness of security measures should not depend upon secrecy of the design of the mechanisms themselves
- people will eventually discover the mechanism anyway
- mechanisms can be reviewed by several experts if they are not secret
What are the two types of protection?
- User-oriented control of access
- Data-oriented control of access
What is User-oriented control of access?
Most common version of this is login. Where control access is down to the user.
Can be bad as passwords can be forgotten or easily hacked as people make easy to guess passwords
What is Data-Oriented Access control?
We try to control which processes can do which operations to which files and programs. We define an object to be anything which access is being controlled.
How does Windows do Data oriented access control?
Each process has an access token and each object has a security descriptor. When a process tries to perform an operation on an object, Windows uses the process’s Access token to check the security descriptor to ensure that this operation is allowed.
