Lecture 14 - Security Flashcards
What is the difference between protection and security?
Protection: control access of resources to processes
Enforces security policies
Security: Prevents unauthorised access to a system
What 5 broad objectives does security aim to provide?
Confidentiality- prevent unauthorised access
Integrity - ensure data has not been modified
Availability - ensure system is accessible
Accountability - know who did what
Authentication - authenticate each user
What is a protection domain?
Defines the objects a process may access and how it may access them
E.g. in domain 1 File1 has [R] access, but in domain two (another process) it might have [RW] access
How does a protection/access matrix work?
Domains down left side files at top
Permissions in intersecting squares
How can an access matrix be compressed?
Associate permissions with each object: access control list
Associate permissions with each domain: capabilities
How are access control lists done on UNIX?
Process permission is specified by the owner of the process
Each file has entry in the list
Each entry has access rights for each owner
In UNIX what 3 domains are ACLs defined for?
File owner
Group
Everyone else
What is a capability?
Each process has a list of capabilities i.e. access rights to an object
How is faking of capabilities prevented?
Cryptographic techniques to encode what each capability allows - can’t impersonate because don’t know how the capability was encoded
Capability lists are privileged instructions
Rely on hardware features
How is revocation of access rights easier in Access Lists than Capability Lists?
Access list - simply delete the rights
Capability - have to find the process and its list before the right can be deleted
What is the difference between discretionary access control and mandatory access control?
Discretionary: each object has an owner, usually creator, who controls the access rights
Mandatory: creator is not owner, and does not control access rights, they are defined by a security policy
What are the 3 forms of authentication?
Something you know - password
Something you have - key card
Something you are - biometric
What is bell-la padula multilevel security model?
Processes and objects have a security level
Process at level k can only read objects at level k or lower and write at level k or higher
Prevents higher level info leaking to lower levels
What is the Biba multilevel integrity model?
Processes and objects have security level
Process can write only objects at its level or lower
Can read only at its level or higher
How can covert channels be used to communicate?
Send data using side effects
e.g. file locking or allocating resources
