sem 3

Question 1

Types of Access Control

Answer 1

1. Mandatory Access Control (MAC)
2. Discretionary Access Control (DAC)
3. Role- Based Access Control (RBAC)

Question 2

What is Mandatory Access Control (MAC)

Answer 2

MAC is access based on security labels and security clearances. A user cannot grant clearance to another person. Only the administrator can grant access to users. MAC is strict and it can be applied in environments where tight control is necessary such as military.

Question 3

Discretionary Access Control (DAC)

Answer 3

it is based on the subject and the access rules that states whether the subjects can perform certain actions on the object.
Subjects have controlled access to their own objects. it is flexible because subjects can grant access to other subjects, but can be too messy

Question 4

Role-Based Access Control (RBAC)

Answer 4

access is based on the role subjects are assigned to and the rules that state which roles have access to which objects.

administrators assign access rights to roles, instead of individual users.

it is less flexible than DAC, but easily manageable because it is centrally-controlled.

Question 5

Draw a general model for File Access

Answer 5

slide 22
- has the subject
- object
- and access right

Question 6

what are the 3 groups that can be granted permission in Linux?

Answer 6

1. User (owner)
2. groups
3. others

Question 7

ls -l /etc/passwd

Answer 7

sees which user has what type of access to the file.

output: rw-r–r– (other stuff.._)

Question 8

id

Answer 8

id command shows us what groups we are assigned to.

Question 9

groups root

Answer 9

helps us to see the members of the group named “root”.

Question 10

touch suss1

Answer 10

creates a file named “suss1”

Question 11

ls -l suss1

Answer 11

shows us the permissions for only filed name “suss1”

output: -rw-rw-r–

Question 12

chmod 765 suss1
ls -l suss1

Answer 12

changes permission for the file that was created by the user or owned by the user.

output: -rwxrw-r-x

Question 13

values of read, write and execute command.

what is the value of
rw-r-xr?

Answer 13

read: 4
write: 2
execute:1

rw-r-xr–:
rw:4 + 2 = 6
r-x: 4 + 1 = 5
r–: 4

Therfore, it should be chmod 654 suss1

Question 14

ls -l suss1
chmod u+x suss1
chmod ug-x suss1
chmod +x suss1

Answer 14

outputs:
-rw-r-xr-
-rwxr-xr–
-rw-r–r–
-rwxr-x-rx–

Question 15

what command do you put if you want to remove write access for user and gain write access for group?

Answer 15

chmod u-w,g+w suss1
ls -l

Question 16

what are the 3 types of security threats for operating systems

Answer 16

1. intruders
2. malicious software
3. Buffer overflow

Question 17

what are the 3 types of intruders?

Answer 17

Masquerader: usually outsider, breaks system access control and pretends to be another user.
Misfeasor: usually insider, user misuses his or her access privileges or access resources he or she does not have access to.
Clandestine: usually insider or outsider, gets root control system and bypasses access control

Question 18

what are the 2 groups of malicious software?

Answer 18

independent: known as a self-contained program, and can be run by the OS (worm)
needs a host program: known as a parasitic, needs to be attached to a host program (virus)

it can destroy files and bypass access control.

Question 19

Explain Buffer Overflow

Answer 19

– can occur because of programming error when a process
attempts to overwrite adjacent memory location
– can result in the attacker able to gain control in the
program
– attacker can use Metasploit against unpatched system
(that is vulnerable to buffer overflow) and get a shell
remotely

Question 20

What are the 3 countermeasures for the 3 security threats mentioned?

Answer 20

1. Authentication
2. Access Control
3. Buffer Overflow Countermeasures

Question 21

Authentication

Answer 21

To identify and verify users or whom they claim to be.

OS can use these information to authenticate:
1. Something you know: username and passwords
2. Something you are: fingerprints
3. Something you have: ATM card

Two or more factors can be implemented to enhance security.

Question 22

Access Control

Answer 22

works hand in hand with authentication

provides the correct access rights after authentication

Question 23

sudo su -
adduser david

cat /etc/passwd

Answer 23

a more user friendly way to add a new user in the Linux OS

last command helps to check if the new user has been successfully added.

Question 24

deluser david

Answer 24

delete the user david

Question 25

see activity 3 in studyguide

Question 26

Buffer Overflow Countermeasures

Answer 26

compile time defence: resist attacks by hardening program
runtime defence: aims to detect and stop attacks in executing programs

Question 27

What is Operating Systems Hardening?

Answer 27

default configuration of the OS can open up many ports and unnecessary services, making it easy for hackers to compromise the system. Therefore, system hardening is necessary.

Question 28

5 Steps for OS hardening

Answer 28

1. installing the OS and patching
2. remove unnecessary ports and applications
3. configure the user, groups and permissions
4. install and configure additional security measures
5. Test system security.

Question 29

why is the first step of hardening OS important: installing the OS

Answer 29

– Proper planning in installing an OS is important
– Minimise the software package included
– Booting process also has to be taken care of (e.g. password
for changes to the BIOS)
– Use of cryptographic file systems

Question 30

why is the second step of hardening OS important: remove unnecessary ports and services

Answer 30

– System planning needs to be done to perform this task to
resolve the conflict of usability and security
– Unnecessary services should not be installed by default

Question 31

why is the third step of hardening OS important: configure user, groups and permissions

Answer 31

– Access control needs to be planned properly so that the
users will not have more privileges than they are required
– Categorisation of users should be done with care
– Additional group that the users are in should be justifiable

Question 32

why is the fourth step of hardening OS important: install and configure additional security controls

Answer 32

-Additional security controls should be implemented (e.g.
antivirus software, host-based firewall, host-based
intrusion detection system, etc.)
– These additional controls are often necessary
– Antivirus software needs to be updated on the definition
files (or signatures)

Question 33

why is the fifth step of hardening OS important: test security measures

Answer 33

– To make sure that what you have implemented works
– Use a checklist (specific to the different OS being used)