← Years 9–10 Digital Systems

Access control lists

A table attached to a resource, like a file or router, that lists which users or groups may access it and what they can do. If you are not listed, access is denied.

Part of: 9-10 Digital Technologies Vic Curric - Digital Systems and Security — Module 21, VCE Data Analytics - U4O2 - Cyber Security: Data Security — Module 49, ACARA Digital Technologies Years 9–10 — Networked Systems and Access Control — Module 119, WA Computer Science ATAR Year 11 — Network Communications — Module 131, WA Computer Science ATAR Year 11 — Cyber Security — Module 111

Understanding Access control lists in Years 9–10 Digital Systems

What it does: The table is attached to the Reports folder and lists each group with the actions it may perform. The router checks each row. Only the listed address is permitted and everything else is denied. ACLs usually deny by default. If a user or group is not listed, they get no access. ACLs are used on file shares and on network devices such as routers and switches to control who or what can get through. Being listed is not enough. Sam can only do the actions in the row, and Read does not include deleting. The ACL belongs to the resource. When someone tries to use it, the system checks the list to decide whether to allow it.

Common mistakes: The comment says students may only read the marks file, so their row must list just read. Giving them write lets them change marks. It should be students: read. An ACL should deny by default. Only the listed devices should be permitted, and everything else should hit the final rule, deny all. Writing permit all lets anyone through.

Class: _____________________  ·  Name: _____________________  ·  Date: _________

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This module's key terms are also in a printable crossword (Modules 13–24) and word search (Modules 13–40).

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Learning
Duo
What does an access control list (ACL) attached to a file do?
Scans the file for viruses and removes themLists which users or groups may access the file and what they can do
Matches
Folder: Payroll Sam: read Sam is not listed so Sam can still open it
↓
Access is denied by default. A user who is not listed in the ACL cannot open the folder.
Applying
Meanings
Term
access control list (ACL)
Meaning
A table attached to a resource, like a file or router, that lists which users or groups may access it and what they can do. If you are not listed, access is denied.
Practice
Resource: HomeworkShare
Testing
Gaps
Everyone else ->
Check Answer
Spots
2teachers: read, write
3students: read, write

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Quick Questions

1. What does an access control list (ACL) attached to a file do?
A. Lists which users or groups may access the file and what they can do ✓
B. Scans the file for viruses and removes them
An ACL is a table attached to a resource. It lists who can access it and what actions they are allowed to take.
2. A file share has this ACL row: Maya | Read. Which action can Maya do?
A. Open and read the files ✓
B. Edit and delete the files
Each row of an ACL pairs a user or group with the actions they are allowed. This row only gives Read, so Maya can view the files but not change them.
3. Jordan is not listed anywhere in the ACL of a shared folder. What happens when Jordan tries to open it?
A. Access is allowed because nobody blocked Jordan
B. Access is denied ✓
ACLs usually deny by default. If a user or group is not listed, they get no access.
4. An ACL row reads: Year10Students | Read, Write. Who does this row apply to?
A. A whole group called Year10Students ✓
B. Only one single student
ACL rows can name a group as well as an individual user. Everyone in the group gets the listed permissions.
5. Which of these is a place where an ACL is commonly used?
A. A keyboard deciding which letters to type
B. A router deciding which devices can reach a network ✓
ACLs are used on file shares and on network devices such as routers and switches to control who or what can get through.

Match the Pairs

alice: read, write → One row of an ACL: the user alice is allowed to read and write this resource.
Everyone: no access → A rule that denies access to all users. Anyone not given permission by another row is blocked.
An ACL on a file share can give a group read-only access to a folder. → Folder: Reports Students: read Teachers: read, write
An ACL on a network device such as a router lists which addresses are allowed in. → permit 192.168.1.10 deny all
Folder: Payroll Sam: read Sam is not listed so Sam can still open it → Access is denied by default. A user who is not listed in the ACL cannot open the folder.
An ACL is stored on each user's phone and lists every file they have → An ACL is attached to the resource, not the user. It lists who can access that one resource.

Key Term

access control list (ACL)
A table attached to a resource, like a file or router, that lists which users or groups may access it and what they can do. If you are not listed, access is denied.

Fill in the Blanks

1. ACL: staff -> read, write ACL: students -> read Everyone else -> deny
Hint: Type the outcome for anyone who is not listed in the table
2. # mia can view the file but not change it mia -> read
Hint: Type the permission that lets a user view only
3. ACL for share Homework: Year9 -> read, write Year10 -> read
Hint: Type the acronym for the table attached to a resource
4. router ACL: permit 192.168.1.10 deny any
Hint: Type the keyword that lets a listed device through
5. router ACL: permit 192.168.1.10 deny any
Hint: Type the word that means every other address not listed

Spot the Error

Question 1
A # Students may only read marks
B teachers: read, write
C students: read, write
D default: deny
Line C — The comment says students may only read the marks file, so their row must list just read. Giving them write lets them change marks. It should be students: read.
Question 2
A Router ACL (checked top down)
B permit 10.0.0.5 to server
C permit 10.0.0.6 to server
D permit all
Line D — An ACL should deny by default. Only the listed devices should be permitted, and everything else should hit the final rule, deny all. Writing permit all lets anyone through.
Question 3
A user: Budget.docx
B finance: read, write
C interns: read
D default: deny
Line A — An ACL is attached to a resource, so the first line should name the resource (resource: Budget.docx). Budget.docx is a file, not a user.
Question 4
A user ← Mia
B IF user is not in the ACL THEN
C allow listed actions
D ELSE deny
Line B — Only users who ARE listed in the ACL get the actions listed for them. The test should be IF user is in the ACL THEN, with ELSE deny for everyone else.
Question 5
A Row: maya, read-only
B Request: maya reads file
C Result: deny
D Request: maya edits file
E Result: deny
Line C — Maya's row lists read, so her request to read the file is allowed. The result should be allow. Her edit request on line 5 is correctly denied.

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