Who deleted the file?
On Friday a shared marks file is gone. Who did it? A student? A teacher? An old account?
If nobody can say, nobody can fix the cause.
The last two steps of the IAAA model solve this. One limits what a person may do. The other records what they did.
By the end of this lesson
Note
I can explain the last two steps of the IAAA model, with the techniques used and their benefits and drawbacks.
Key words
| Word | What it means | Example |
|---|---|---|
| Authorisation | Making sure a logged-in user can only do what they are allowed to do. | |
| Role-based access | Access set by a person's job in the system. | teacher |
| Access control list | A list that says which users may do which actions on one resource. Short form: ACL. | |
| Resource | A file, folder, printer or system that can be used. | |
| Accountability | Any action can be traced back to the user who did it. | |
| Audit log | A record of who did what, and when. | |
| User activity monitoring | Watching what users do in a system. | |
| Least privilege | Giving each person only the access they need. | |
| Shared account | One login used by many people. |
The cells students fill in are left blank in this preview.
Starter: what you already know
Have a go
Starter: what you already know
3 questionsYour answers are marked here and are not kept. A college account keeps every student’s marks.
Cycle 1: authorisation
Authorisation comes after login. The system now knows who you are. It decides what you may do.
The aim: an authenticated user can only reach the resources and do the actions they are allowed to.
This follows least privilege. A student may read a lesson. Only a teacher may change it.
Role-based access and ACLs
Role-based access gives rights by the role. Everyone in the teacher role gets teacher rights. When someone changes job, you change their role.
An access control list is attached to one resource. It lists exactly which users may do which actions.
Roles are easier for many people. ACLs are finer for one file.
Worked example: roles and an ACL
| Who | Role-based: any file | ACL on marks.xlsx |
|---|---|---|
| Student Sam | Read lessons only | No entry: no access |
| Teacher Aisha | Read and write lessons | Read and write |
| Teacher Raj | Read and write lessons | Read only (added by the head) |
| Admin Lee | Read, write and delete | Read and write |
The cells students fill in are left blank in this preview.
Cycle 2: accountability
Accountability means every action can be traced back to the person who did it.
It needs: unique logins (no shared accounts), audit logs that record who did what and when, and user activity monitoring that watches for odd behaviour.
Logs must be protected. If an attacker can delete the log, the trail is gone.