Access control and least privilege

Least privilege

• A core security rule: give every person and program only the access they need — no more.
• If an account is broken into, least privilege means the attacker can reach less.

Access control on files

• On Linux, file permissions are access control in action (you met these in the Linux course).
• ls -l shows who can read, write, and execute, for the owner, the group, and everyone else.

ls -l secret.txt

Locking down a secret

• A file holding a password or key should be readable by its owner only.
• chmod 600 gives the owner read+write, and nothing to anyone else:

chmod 600 secret.txt

• 6 = read+write for the owner; 0 and 0 = no access for group and others.

Your turn

• Lock down secret.txt so only its owner can touch it. Good permissions are a simple, powerful defence.

Covers: A-Level 6.1 (access levels / security measures).

Common mistakes

• Give each user only the access they need (least privilege).
• Do not use an administrator account for everyday work.