--- title: "Who are you, and what may you do?" subtitle: "Security and privacy · How systems are kept safe · Lesson 3" --- # Who are you, and what may you do? **Name:** {{field-24}} **Date:** {{field-15}} **Class:** {{field-15}} > **Key question:** You and your teacher both sign in to the same school system. Why can your teacher change marks and you can't? :::teacher-note **In one sentence:** Students sign in as different users, try to read and change files, switch on multi-factor sign-in and fix a permissions table, to distinguish authentication from authorisation and apply least privilege (AC9TDI10K01 node 3). **Students should be able to say:** I can explain the difference between authentication and authorisation. I can explain why multi-factor sign-in is safer. I can set permissions so each role has only what it needs. **Width:** the unmarked parts are the floor every student does (predict, run, investigate and make). Typical adds the modify practice; wider adds the real-world contexts. They add contexts, not difficulty. Students work in the online tutorial alongside this sheet. ::: ## Predict :::keep-together **Sam the student signs in with the right password, then tries to change the class marks. What happens?** ☐ It works, but only for Sam's own mark ☐ Denied: signing in proves who Sam is, but students aren't allowed to change marks ☐ Sam is signed out ☐ It works: Sam signed in correctly My prediction, and why: {{lines-3}} ::: :::teacher-note **What happens:** Denied. The password proved it is Sam (authentication); the permissions say students may only read Marks (authorisation). ::: ## Run Try it on the board in the tutorial. Was your prediction right? What was different? {{lines-2}} ## Worked example: two checks :::keep-together ### One request, two checks 1. $\text{Sam types "maple"}$ — Authentication: is the password right for Sam? 2. $\text{signed in as Sam (student)}$ — The system now knows who is asking. 3. $\text{"change Marks"}$ — Authorisation: what may students do with Marks? 4. $\text{Students: Marks = read}$ — The permissions table says read only. 5. $\text{denied}$ — Signed in, but not allowed. Least privilege: each role gets only what its job needs. Now name the authentication step. **Which is **authentication**?** ☐ Logging out ☐ Being allowed to read a file ☐ Typing your password to prove who you are ☐ Changing the permissions table ::: :::teacher-note **Answer:** Typing your password to prove who you are Authentication answers "who are you?"; authorisation answers "what may you do?" ::: :::keep-together ### Find the mistake **Sam explains what signing in allows. Click the line where it first goes wrong.** ``` 1 Sam signs in with the right password. 2 So the system knows it really is Sam. 3 So Sam is allowed to do anything on the system. 4 So Sam can change the class marks. ``` Line: {{field-15}} Why is it wrong? {{lines-2}} ::: :::teacher-note **Answer:** line 3 Line 3: signing in only proves who Sam is. What Sam may do is a separate check, the permissions for students. ::: :::keep-together ### Why multi-factor? **Why add a code from a phone (multi-factor sign-in)?** ☐ It replaces permissions ☐ It speeds up signing in ☐ A stolen password alone is no longer enough to get in ☐ It makes the password shorter ::: :::teacher-note **Answer:** A stolen password alone is no longer enough to get in An attacker would need your password and your phone. ::: :::typical ## Vary: one change at a time **A teacher.** **Wrong password.** **Multi-factor.** **The admin role.** Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} ::: ## Access control :::keep-together ### Sort them **Authentication (who are you?) or authorisation (what may you do?)** Groups: Authentication, Authorisation - Typing a password: {{field-15}} - A fingerprint unlock: {{field-15}} - A code from an app on your phone: {{field-15}} - Students may read but not change Marks: {{field-15}} - Only the class teacher can open the gradebook: {{field-15}} - A shared folder set to view only: {{field-15}} ::: :::teacher-note **Answer:** Typing a password → Authentication; A fingerprint unlock → Authentication; A code from an app on your phone → Authentication; Students may read but not change Marks → Authorisation; Only the class teacher can open the gradebook → Authorisation; A shared folder set to view only → Authorisation Proving identity is authentication; rules about actions are authorisation. ::: :::keep-together ### Strong passwords **Which password is strongest?** ☐ maple ☐ Password1! ☐ purple-otter-sings-at-dawn ☐ 12345678 ::: :::teacher-note **Answer:** purple-otter-sings-at-dawn Length beats tricks: a long passphrase of unrelated words is hard to guess and easy to remember. ::: :::keep-together ### Review: DNS **Review: what does DNS do?** ☐ Encrypts web pages ☐ Blocks phishing ☐ Turns a name into an IP address ☐ Checks passwords ::: :::teacher-note **Answer:** Turns a name into an IP address It is the internet's address book. ::: ## Make: least privilege Then: which account would an attacker most want to steal, and how would you protect it? Work in the tutorial. Plan first: what will you change, and how will you test it? {{box-4}} ## Exit ticket :::keep-together **Give one example of authentication and one of authorisation. Why use multi-factor sign-in?** {{lines-3}} ::: :::teacher-note **Answer:** Authentication: a password or fingerprint. Authorisation: students may only read marks. MFA means a stolen password alone isn't enough. :::