Blog article

Zero Trust Authentication: Never trust, always verify

Learn about zero trust authentication, where nothing is trusted by default. Access is only granted based on identity, device health, and context.

Petr Pecha


Min read

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Zero trust architecture has become increasingly popular in recent years as more and more organizations look for ways to improve their cybersecurity posture.

In a zero trust architecture, every user and device must be authenticated and authorized before being granted access to the network, application, or resource.

This article discusses the main pillar of zero trust: authentication.

Table of contents

What is zero trust authentication and why is it important?

Authentication is arguably the most important mechanism in the zero-trust model of network security. In a zero trust environment, nothing is trusted by default. Access is only granted based on identity, device health, and context.

How does zero trust authentication work?

The mechanism of zero trust authentication includes three main steps.

  1. The user must prove their identity with username, password, and additional identity factors (more about that later).
  2. The device they are using to access the network is also authenticated to ensure it complies with the organization’s security policies.
  3. Once both the user and device have passed authentication, they are authorized for access to the desired resource. This involves the assignment of pre-defined access privileges.
Fig. 1 – In zero trust architectures both users need to be authenticated before access privileges are assigned.

Why is zero trust authentication important?

Zero trust authentication helps organizations to reduce the risk of unauthorized access, and thus prevent data breaches and other security incidents. By implementing the zero trust model of authentication, organizations ensure that every user and device is verified before being granted access to sensitive data or internal resources.

This practice reduces the organization’s attack surface, making it harder for cybercriminals to infiltrate the network and cause harm.

Key principles of zero trust authentication

Identity verification

Every user and device requesting access to a resource must be identified and verified before access is granted.

This involves verifying the user identity and the device’s legitimacy for access.

In zero trust user authentication is identity-based, which means it determines to a high degree of certainty that the user is who they claim to be.

This is different from signing in to services like online discussion forums, where you choose a nickname and a password. In such a scenario, you interact more or less anonymously. In identity-based authentication, user electronic identity is agreed upon and often explicitly provided by the company.

To do this, companies often rely on some source of identity. A source of identity can be provided by SSO (single sign-on) or, in larger companies, IAM (identity and access management). Both these solutions centralize user management, allow admins to add or remove users, and assign access rights.

Device authentication

Device authentication in zero trust verifies the device’s legitimacy for access. Methods used for device authentication can involve certificates installed on the device, client apps, or hardware tokens. Biometrics are sometimes used as well, for both user and device authentication.

Many zero-trust solutions also perform device posture checks, which check for the OS version, vulnerability patches, antivirus software, and more.

Continuous authentication

Once a user and device are authenticated and authorized, their access to resources is monitored throughout the entire session. The objective of this monitoring is to spot anomalous behaviors and adapt to changing context.

If these anomalies threaten the user’s legitimacy for access, re-authentication is triggered.

Multi-factor authentication

Multi-factor authentication (MFA), formerly two-factor authentication (2FA), is a security mechanism that requires users to provide multiple forms of identification to gain access to resources. This could include a password and one-time passcode, an action via an authentication app, or a biometric identifier, such as a fingerprint or face scan.

MFA is an effective way of preventing unauthorized access via compromised login credentials. Even if an attacker steals the username and password, they cannot gain access unless they also provide additional identity factors.

Context-based authentication

Also known as risk-based authentication, context-based authentication evaluates the risk associated with a user or device requesting access to a resource and applies appropriate authentication measures based on that risk.

Stricter policies are then applied depending on the context of the authentication attempt, e.g. from a new location, during unusual time, or with an unknown device. For example, when a user is trying to access resources in the evening, stricter authentication methods will be applied than when accessing during normal business hours.

Least privilege

Once users have been authenticated, they are authorized for access to systems. Under zero trust, authorization follows the least-privilege principle.

According to the principle of least privilege, users and devices are granted access to only the resources they need to perform their tasks. This principle ensures that even if a user or device is compromised, the impact of the attack is limited to the resources that they have access to.

The least-privilege principle provides several benefits:

  • Reduced attack surface – The least-privilege principle reduces the impact of a successful compromise by a cyber attacker, and the amount of data at risk of misuse or exposure.
  • Less room for lateral movement – Following the least-privilege principle places obstacles in the path of a cyber attacker on the way from their initial point of entry to their ultimate objective.
  • Less room for error – Giving users access only to a limited pool of systems also reduces the risk of damage caused by user negligence.

In terms of network architecture, the least-privilege principle translates to segmentation.

Challenges of implementing zero trust authentication

Implementing zero trust authentication is not without challenges. Here are a few of the most common challenges that businesses face:

  • Integration with legacy systems – Existing systems may not support modern authentication protocols such as OAuth 2.0, OpenID Connect, or SAML.
  • User resistance to change – Implementing zero trust authentication requires users to learn new processes and adopt new behaviors.
  • Management complexity – Managing multiple authentication mechanisms can be difficult and time consuming, especially for companies with a large number of users and systems.
  • Costs – The purchase of new cybersecurity solutions and hiring new staff can strain the budget of organizations, especially small and medium ones.
  • Reduced productivity – It can be challenging to design the zero trust authentication process in a way that doesn’t hinder employee productivity but still enforces a strict security standard.

How to overcome the challenges of implementing zero trust

Mature zero-trust solutions, like GoodAccess, provide zero-trust technology as a service.

We have bundled user pre-authentication, threat protection, least-privilege access controls, MFA, and application-level visibility into a SaaS service that is easy to deploy and use even if you don’t have a trained IT specialist on staff.

You can try all of its features for 14 days for free here. If you need any assistance, our specialists are on standby to help you.


Authentication is a critical component of zero trust architecture that is essential for improving cybersecurity and reducing the risk of data breaches and other security incidents.

Even though implementing zero trust authentication can be challenging, overcoming the hurdles and embracing the trend will significantly improve the security posture of organizations, protect their customers and data, and ensure compliance with regulations like NIS2.

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