Least privilege and zero trust

Two ideas that limit the damage

Most security is not about building one perfect wall. It is about making sure that when something does go wrong, the damage stays small. Two ideas do much of that work: least privilege (give only the access that is needed) and zero trust (verify every time, do not assume). They fit together, and neither needs you to be a technical expert to understand.

Least privilege: only what the job needs

Least privilege means each person, and each app, gets exactly the access their role requires, and no more. A new colleague in accounts needs the finance system, not the keys to the servers. A newsletter tool needs to send email, not to read every file in the company.

The reason is what happens when an account is misused, whether by a mistake or a stolen password. Security people call it the "blast radius": how far the damage can reach. If a compromised account could touch everything, the blast radius is the whole organisation. If it could only reach the few things one job needs, the same break-in stays small and contained. This is really a careful use of authorization: granting each person just the permissions their work calls for.

It also means tidying up over time. Access granted for a project last year should be removed when it is no longer needed, so permissions do not quietly pile up.

Zero trust: verify, do not assume

The older way of thinking drew a line around the office network and treated everything inside it as safe. The problem becomes obvious once an attacker gets in, or a laptop is stolen, or people work from home and cafes: "inside" stops meaning "trusted".

Zero trust replaces the assumption with a habit: verify each time, no matter where the request comes from. Every access is checked on its own, based on who is really asking and whether they should have this particular thing right now, rather than on which side of a wall they happen to be. Being on the office network is no longer a free pass.

The two working together

Least privilege and zero trust reinforce each other. Least privilege keeps the set of things any one account can reach small. Zero trust keeps checking that each request is really allowed, every time. Together they mean a single stolen password or one careless click reaches far less, and gets challenged along the way.

A homely version: you would not hand every visitor a master key just because you let them through the front gate. You give them the one key they need, and you still check it at each door.

Check yourself