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Zero Trust Principle

Zero trust is a security principle built on the idea of never trusting and always verifying, requiring continuous authentication and authorization rather than granting blanket access based on network location. It addresses weaknesses in traditional perimeter-based security by checking every user and device on an ongoing basis.

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About this video

Zero trust is a security principle that rejects the assumption of implicit trust within a network, operating instead on the rule of never trust, always verify. Traditional network security models treat internal access as inherently safe, authenticating users or devices once at the boundary and allowing relatively free movement inside. This is comparable to a venue that checks IDs at the door but never again once guests are inside, assuming everyone present has already been vetted. Zero trust challenges that model by requiring verification to be continuous rather than one-time. The practical implications of zero trust extend beyond network connectivity into identity and access management. In conventional environments, a user who logs in receives an access token that reflects their permissions at that moment, meaning changes to their role or status may not take effect until they log out and back in. This creates windows of residual access that can be exploited, whether through insider misuse or during employee offboarding. Under zero trust principles, access is verified each time a resource is requested, so permission changes take effect immediately and stale access is eliminated. While the principle itself is straightforward, implementing zero trust across an organization involves both architectural decisions and supporting technologies designed to enforce continuous verification at scale. The principle applies broadly across security domains, but network architecture in particular has developed dedicated frameworks and tooling to put zero trust into practice. Understanding the principle is the starting point for evaluating those frameworks and technologies effectively.

What you'll learn

Explain the zero trust security principle of 'never trust, always verify' and contrast it with traditional perimeter-based network security models
Describe how continuous verification applies to both network access and resource-level authorization in a zero trust environment

What's covered

Zero Trust Principles

Core Principle
- Never Trust Always Verify
- Defense in Depth
Traditional vs Zero Trust
- Traditional Single Firewall
  - Trust Once Inside Network
- Continuous Verification
  - Ongoing Checks Required
Zero Trust Use Cases
- Network Access Control
  - Unauthorized Device Example
  - Infected System Example
- Resource Permission Changes
  - Token Based Access Issue
  - Role Change Scenario
Implementation Considerations
- Beyond Networking
- Supporting Architectures
- Supporting Technologies

Key terms

Zero Trust: A security model that assumes no user or device is trusted by default and requires continuous verification.
Authentication: The process of verifying the identity of a user, device, or system.
Authorization: The process of determining what actions or resources an authenticated user is permitted to access.
Least Privilege: A security principle that grants users and systems only the minimum access rights needed to perform their functions.
Network Segmentation: The practice of dividing a network into smaller segments to improve performance and limit the spread of security threats.
Continuous Verification: The ongoing, repeated process of authenticating and authorizing users and devices each time they request access to a resource, rather than only at initial login.

Topics

Zero Trust Network Security Identity Verification Access Control Perimeter Security Cybersecurity

Transcript

One way we can really practice defense in depth is by putting into place zero trust principles.

One thing to understand about zero trust is that we have a principle that we work by. But there's also an architect, and there are technologies that help support this. Right now our focus is fully on just the principle of zero trust.

Never Trust, Always Verify

The zero trust principle is simply this: never trust, always verify. In traditional networks, as we talked about, we will have a single firewall and we would protect our systems in here. We would assume that once a system connects into our system, it's a trusted system and has access to certain resources on this network based off the fact that it's inside of that network.

Let me give you an example of this. Let's say there is a bar or some sort of nightclub that only allows people that are over 21 to access that club. Think of the bouncer. The bouncer is at the front door and they're going to check your ID to make sure you're of age to be able to get into that environment. But once you are in that environment, they're not going to continually check your ID within that environment. This is more of the traditional way of thinking, because you're saying, well, we've already verified you before you've entered into the club, and so now we know that you're safe and you can be in the club, that you're of age.

Zero trust says we are not going to trust that, even though you're inside of this network, because there are things that can happen. For instance, somebody could plug into the network that is not authorized to be on this network, or a system that was fine before now gets infected and is not fine now. So what are we going to do? We're going to continually check, making sure that you don't have viruses on your machine and you're all up to date, or whatever the case may be, on a continuous basis. Not just once, but we're going to continue to do that.

Beyond the Network

Now, this doesn't have to do just with networking as well. It's not just whether the switch is going to allow you to communicate across this network. Let me give an example here. In some systems, like Windows, what would happen is you would be given a token for accessing certain resources. So Juan logs in on this computer and is given access to whatever files and folders that they need to have access to.

But let's say something changed. Let's say Juan now is promoted and moves up into management. He no longer needs access to sales, but does need access to management. Well, the problem is that Juan would still have access to sales and not have access to management until he logs off of his computer and logs back on, and now has access to management. You could see how this could be a problem, especially if we were laying somebody off and they still had this residual access on the system.

This idea of continually check and verify means that every time Juan accesses sales, it will still verify and say, okay, you're Juan, but do you still need access to sales? Should you still have access to sales? And when we make this switch to management, then he would no longer have access to sales and would now have access to management in a zero trust environment, because a zero trust environment is never trust, always verify.

That is the principle that we want to implement on our network when we're architecting our network. But there is a whole official architect for this, and there are technologies that help support that architect to support this principle. We could really apply this principle in a lot of different areas, but when it comes to networking, there are specific architects and technologies that will help us implement this type of principle.

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