Why ZTNA is replace of VPN?

Many people tend to say that ZTNA (Zero Trust Network Access) is a substitute for VPNs.
What do they have in common, and what are the key differences?
More importantly, why do people make this comparison?

Let’s take a closer look at how ZTNA differs from traditional VPNs.

1. Authentication process

The first difference lies in the authentication process.
In a Zero trust model, authentication is significantly strengthened.

With traditional VPNs, authentication is typically based on ID/password or OTP.
With ZTNA, access is denied if the device has not been pre-approved.

2. Scope of access

There is a difference in the scope of access after authentication.
As the name suggests, VPN stands for "Virtual Private Network" and is a network-based solution.

Once connected to a VPN, users can access all network resources within the internal network.
However, ZTNA focuses on "network access" at the application level, following the Zero Trust principle of trusting no one by default.

3. Continuous Authentication in ZTNA

When discussing ZTNA, the concept of continuous authentication is often misunderstood.
Some assume it means users are required to repeatedly enter their ID, password, or OTP every time they attempt to access additional resources, which would clearly degrade the user experience.

However, continuous authentication in ZTNA has a very different meaning.

Even after a user successfully completes the initial authentication by meeting all required conditions, ZTNA continuously evaluates the security posture of the device throughout the session. If any of the predefined conditions change, access can be revoked, or re-authentication can be enforced—even for an already authenticated session.

For example, a user may initially pass authentication because their device meets all security requirements, such as having an active antivirus program. If that antivirus is later disabled or removed during the session, ZTNA can detect the change, immediately terminate the session, and require re-authentication before allowing further access.

This continuous verification model ensures that trust is never permanent and is always reassessed based on real-time security conditions.

Conclusion

So far, we have explored the key differences between traditional VPNs and ZTNA.
Through this comparison, it becomes clear why ZTNA is often considered more secure than VPNs and is frequently described as a replacement rather than just an alternative.

By enforcing strict authentication, limiting access at the application level, and continuously verifying security conditions, ZTNA fundamentally changes how access to internal resources is protected.