Homework #8 Solution

Assignment: Problems 18.1, 18.11, & 3 Prof Bill questions

Problem 18.1

What are the main differences between capability lists and access lists?

The access list for an object lists the domains which contain the access rights for the objects.

A capability list describes, for each domain, the access rights for each object in that domain.

The difference between these two constructs is how their information is organized. Access lists are organized by object (the columns in an Access Matrix) and capability lists are organized by domain (the rows in an Access Matrix).

 

Problem 18.11

What is the need-to-know principle? Why is it important for a protection system to adhere to this principle?

The need-to-know principle states that a process should only be allowed access to resources for which it has authorization and that it currently needs to complete its task.

By adhering to the need-to-know principle, the damage created by a faulty process (via a bug or malicious code) is limited to its "need-to-know" resources, not some larger set.

 

Ch 18 Unix protection question

What is the difference between having a file's setuid bit "on" and "off"? Give an example of a program that you (a regular user, not superuser) might create where the setuid bit is on.

The setuid bit determines the user-id (or owner, as treated by the operating system) of a running process.

If the setuid bit is off, then the user-id of the running process is the same as the user who started program execution.

If the setuid bit is on, then the user-id of the running process assumes the identity of the owner of the program file.

An example of a program where I would have the setuid bit turned on is a program that accesses a local database file to which only I have write access.

 

Ch 19 System threats question

What is the difference between a worm and a virus? Which is a more dangerous threat to system security?

A worm is a standalone program, while a virus is code embeded in another (host) program.

This is a subjective question, but worms and viruses are equally dangerous threats to system security, in my opinion.

 

Ch 19 Windows NT security question

Describe 3 security features in Windows NT

Three security features in Windows NT:
  1. Upon logging on, users are issued a security access token. The security access token determines the groups to which each user belongs and any special privileges that that user may have.
  2. By default, Windows NT requires a password when logging on to the system. The modular design of Windows NT, however, allows system administrators to add custom authentication packages like fingerprinting or a retinal scanner.
  3. Windows NT has many auditing programs/features built in. For example, system administrators can track login failures to track potential break-in threats.