ZTNA: Zero Trust Network Access

Zero Trust Security: Principles and Framework Explained

What is Zero Trust Security?

Historically, many organizations have used a “castle and moat” approach to managing access to their networks and IT assets. Under this model, the company heavily defends its network perimeter and assumes that anyone inside it is legitimate and trusted.

In 2010, John Kindervag of Forrester Research developed the zero trust security model to address the deficiencies with this approach to access management. It applies the “never trust, always verify” philosophy to access management, individually verifying each access request against role-based access controls.

Main Principles of the Zero Trust Security Model

The zero trust security model is a framework for developing a more secure identity management strategy. It’s based on a few fundamental principles, which include the following:

Identity-Centric Security

Zero trust security is centered on identities. Every entity within an IT environment is assigned an identity, and the same identity is used throughout the organization’s entire IT infrastructure.

Strong identity management is essential to effective access control. Centralized, consistent identity management reduces the risk that a user or device will accidentally be granted permissions that they shouldn’t have or accidentally retain them after they should have been revoked.

Strong Authentication

Tracking user identity provides little benefit if a system can’t verify that someone is who they claim they are. Strong authentication is vital to an effective zero trust system.

In a zero trust model, authentication isn’t limited to the user, who should be authenticated with something more secure than a password. Zero trust systems may also authenticate devices and use these identities to determine access.

Least Privilege Access

The zero trust security model is based on the principle of least privilege. Least privilege states that users, applications, and devices should only be granted the permissions required for their role.

The purpose of least privilege access is to minimize the potential damage a user account can do if it is compromised by an attacker or abused by its owner. A user who only has access to their own computer and lacks elevated privileges can do very little damage to the organization as a whole.

Continuous Verification

The zero trust security model also evaluates access requests on a case-by-case basis. If a user requests access to a resource, that request is assessed based on the permissions and privileges assigned to them. If approved, the user is granted only the requested access for the duration of a single session.

Like least privilege, case-by-case authorization limits potential damage. Users cannot access resources they lack authorization for, and it is much more difficult for an attacker to take over an abandoned session or move laterally through a network without detection.

How Does Zero Trust Security Work?

The zero trust security model is designed to ensure that every access request is legitimate before it is permitted. Every user, application, and device in an organization can have permissions assigned to it, and access requests are evaluated based on these permissions.

To ensure that every access request is authenticated, a zero trust security architecture must be able to intercept and inspect each request. To do so, microsegmentation creates a trust boundary around each application or system. A request must be authenticated to cross the boundary, allowing an organization to control access to that resource granularly.

The Zero Trust Architecture

Zero trust is a security framework built around a few core principles. A zero trust architecture implements these principles in a usable fashion and typically includes the following core elements.


A zero trust architecture evaluates each access request against policy controls before approving or denying it. To do so, it needs the ability to intercept, evaluate, and allow or block access requests en route to their destination.

Microsegmentation creates network boundaries around an organization’s IT assets using software-defined networking (SDN). The system can evaluate access requests at these boundaries and approve or deny them as needed.

Multi-Factor Authentication (MFA)

A zero trust architecture depends on the ability to accurately determine the identity of a user, device, or application. Once it has done so, it can apply the appropriate access controls and policies to the request.

Multi-factor authentication (MFA) offers stronger user authentication than passwords or other single-factor authentication solutions. By requiring multiple authentication factors, MFA reduces the risk that attackers can compromise and use a legitimate account in their attacks.

Zero Trust Network Access (ZTNA)

A zero trust framework should support an organization’s users and IT systems. This includes on-prem and off-site devices, remote workers, and the cloud.

Zero trust network access (ZTNA) offers secure remote access that complies with zero trust principles. Users are only granted access to applications and systems that they legitimately need rather than the corporate network as a whole.

Real-Time Monitoring and Enforcement

Zero trust introduces security and access management into the process of accessing any corporate IT resource. Instead of inherently trusting insiders, a zero trust framework applies the “never trust, always verify” principle.

To do so, the system needs support for real-time monitoring and policy enforcement. Traffic crossing the boundaries defined by microsegmentation should be inspected and evaluated without significantly impacting system performance or the user experience.

Benefits of the Zero Trust Model

The zero trust security model aims to implement more granular access controls for an organization’s resources. This can provide numerous benefits for the business, including the following:

Enhanced Security Posture

A zero trust security architecture strengthens access controls for an organization’s resources. Every request is evaluated independently based on least-privilege access controls before the use of corporate resources is permitted.

This approach to identity and access management enhances an organization’s ability to detect and remediate cyber threats within its infrastructure. Even if an attacker gains access to a system or user account, their ability to move laterally through the network and achieve their objective is limited.

Deeper Visibility

A zero trust security model moves from a “castle and moat” security model to one based on microsegmentation. Instead of evaluating access requests only at network boundaries, every access request is individually validated.

As a result, an organization has a much better picture of the activities being performed within its IT environment. Not only is this beneficial for security, but it can also be used to optimize an organization’s IT infrastructure based on usage patterns.

Improved User Experience

The zero trust model provides access to corporate resources based on need-to-know. Least privilege access controls are applied to each request, and only legitimate ones are blocked.

As a result, the permitted requests flow over the corporate network can be more limited, and users only have access to the resources they legitimately can use. This can reduce congestion on the corporate network and can reduce frustration for users attempting to access resources that they lack permission for.

Enhanced Regulatory Compliance

Most companies are subject to several regulations designed to protect sensitive data. This includes particular types of data — such as payment card information or healthcare data — or the personally identifiable information (PII) of citizens of certain jurisdictions.

One of the most common requirements of these regulations is that an organization controls access to the protected data. Zero trust simplifies this because every request for access to this data is evaluated and logged by the zero trust architecture.

Zero Trust Maturity

According to the Cybersecurity and Infrastructure Security Agency (CISA), there are five main pillars of zero trust, including identity, devices, networks, applications & workloads, and data. As an organization’s zero trust program matures, they build more sophisticated processes and solutions for each of these pillars and across them.

As organizations move through their zero trust journey, CISA defines four main maturity stages, including:

  • Traditional: At this stage, a company primarily relies on manual processes to implement zero trust and least privilege at provisioning and focuses on one of the five pillars at a time.
  • Initial: The organization begins to automate identity management processes, implements cross-pillar solutions, and updates and adapts least privilege access controls after provisioning.
  • Advanced: The organization uses automation when applicable to manage cross-pillar configurations and policies and response to certain incidents, achieves centralized visibility and identity management, and uses risk assessments to update least privilege controls and policies.
  • Optimal: The organization achieves fully automated attribute management, self-reporting, least privilege access control, and continuous monitoring.

Zero Trust Use Cases

Zero trust security offers highly granular control over an organization’s IT assets. This can be used to address various business challenges, including the following:

Secure Remote Work

As remote and hybrid work grows more common, it introduces additional cybersecurity risks to an organization. Remote endpoints may lack the same protections as on-site devices and be vulnerable to malware infections or account takeover attacks.

Zero trust limits the potential risks of a compromised remote worker’s computer or account. Even if an attacker gains access to an organization’s environment, every access request is evaluated against corporate policy, increasing the difficulty of performing malicious actions.

Cloud Security

Companies are increasingly moving data and applications to cloud environments. While this has its benefits, it also introduces additional cybersecurity risks and complexity.

One of the main challenges of cloud security is managing access within and across cloud environments. Implementing a zero trust security policy enables an organization to enhance and standardize cloud access management policies.

Internet of Things (IoT) Security

Internet of Things (IoT) devices are also a growing part of corporate cloud environments. This includes both consumer IoT devices — such as smart thermostats or Internet-connected cameras — and industrial IoT devices designed to control manufacturing systems.

Often, these IoT devices have poor security and can act as an entry point for an attacker to gain access to the corporate IT environment. Zero trust security helps to lock down access to and from these devices, minimizing their potential threat to the organization.

Third-Party Risk Management

In addition to employees, companies commonly grant third parties access to their environments. This includes contractors, vendors, and partners who have a legitimate need to access, manage, or monitor certain systems.

This third-party access introduces the potential for supply chain attacks in which an attacker with access to a partner’s environment leverages their access to target an organization. With zero trust security, an organization can limit these third parties’ access to the minimum necessary, decreasing the potential risk and implications of a supply chain attack.

Threat Detection and Response

Cyber threat actors use various methods to access an organization’s environment and achieve their malicious goals. Account takeover attacks — enabled by phishing or malware — are a common method for cybercriminals to gain initial access to a target environment.

Zero trust limits the risk of account takeover attacks and can expedite the process of identifying and remediating cyber threats. With visibility into every request for access to corporate resources, a security team likely has multiple opportunities to identify and block a data breach or other security incident before it occurs.

Regulatory Compliance

Regulatory compliance is a major concern and significant challenge for many organizations. With large volumes of data scattered across multiple locations, it can be difficult to track and manage access to sensitive, protected data.

Zero trust helps an organization to maintain and demonstrate regulatory compliance due to the visibility it provides into requests for access to corporate resources. The ability to individually authenticate each access request provides opportunities to block unauthorized ones, and access logs from zero trust systems can be invaluable for demonstrating compliance or investigating a successful data breach.

Best Practices for Zero Trust Adoption

Implementing zero trust is a process, and it can be difficult to know where to get started. The following best practices are essential to implementing an effective zero trust architecture.

Define Business Goals

A zero trust architecture can provide various benefits to an organization. However, different businesses may implement zero trust for various reasons.

The first step in the zero trust implementation process is defining business goals and getting buy-in for the zero trust deployment. High-level management support and endorsement are essential to an effective, sustainable zero trust program that spans the entire organization.

Implement Zero Trust Architecture

A zero trust strategy is only effective if it is supported by zero-trust-compatible technologies. If an organization’s networking and security solutions can’t support the granular access controls required by zero trust or are specific to a particular environment — like a cloud platform — then enforcing zero trust security rules will be difficult or impossible.

When implementing a zero trust architecture, it’s important to consider whether existing solutions are able to support it or require replacement. For example, virtual private networks (VPNs) lack the granular access controls mandated by zero trust and should be replaced by zero trust network access (ZTNA) or similar solutions.

Define Roles

A zero trust security strategy is defined based on least privilege access controls. These limit user, application, and device access to the minimum required for a particular role.

Properly defining roles is a crucial component of an effective zero trust deployment. Too broad of roles offer unnecessary access, while too restrictive of roles could negatively impact performance and complicate identity management. Roles should be scoped to fit the needs of a particular entity without being overly restrictive.

Monitor and Refine

A zero trust architecture provides deep visibility into operations performed within an organization’s IT environment. However, this visibility is of limited use if the company doesn’t review and use this data.

Regular monitoring of access logs can enable the organization to detect potential cybersecurity incidents or other unauthorized use of corporate systems. It also enables the organization to identify and correct access controls and policies that do not fit the organization’s business goals or align with the roles of employees, devices, or applications.

Cato and Zero Trust

There’s no doubt that zero trust is the future of access management. It offers organizations the ability to reduce cybersecurity risk and better control access to their IT assets. However, implementing and enforcing zero trust consistently across an organization’s diverse IT environments can be a significant challenge.

The most effective method for implementing zero trust at scale is as part of a Secure Access Service Edge (SASE) deployment. SASE combines ZTNA with other core networking and security functions into a converged, cloud-based security solution.

Cato Networks pioneered SASE and offers a global SASE network backed by a Tier-1 private backbone. Learn more about the zero trust capabilities of SASE.