Access control

Access control decides who can do what. The rule underneath all of it is least privilege: give each person and program only the access they need for their job, and nothing more. When an account is stolen, the damage is limited to what that account could do.

Role-based access control (RBAC) gives permissions to roles, not to people one by one: "Payroll" can read salaries, "Support" can view customer orders. People get roles. When someone changes job, you change their role, and their access follows.

Admins use two accounts: a normal one for email and the web, and a separate admin account only for admin work. Phishing and malware usually arrive through email and browsing, so they land in an account that can't do much. The same idea applies on Linux with sudo: you work as yourself and ask for admin rights for one command at a time.

Separation of duties splits risky jobs so one person can't do it all: the person who adds a new supplier isn't the one who approves paying them. It stops fraud and catches honest mistakes.

Access grows quietly. People move teams and keep old permissions, contractors finish and their accounts stay. So join, move and leave every account on purpose: remove access the day someone leaves, and review who has what every few months. Service accounts (used by programs) and shared accounts need owners too, or they live forever.

Zero trust is the idea that being inside the office network shouldn't make you trusted. Every request is checked: who's asking, from which device, is it healthy, and do they need this? It came about because people now work from anywhere and attackers who get in once used to roam freely.