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Appgate CybersecurityJuly 16, 2021

VPN Limitations Escalate Secure Access Challenges: Best Practices for Moving to Zero Trust Network Access

This blog is the first of a three-part series on how to augment or replace your VPN with Zero Trust Network Access. It discusses why VPN limitations and recommends a five-step approach. Blog 2 reviews the necessary preparation steps for migration and the third blog outlines the steps for successful implementation.

Organizations realize it’s time to augment or replace their virtual private networks (VPNs). VPN limitations render this decades-old technology incapable of handling the security challenges of today’s globally distributed workforce and escalating threat landscape. Zero Trust Network Access (ZTNA) is the modern industry standard for secure access to anything from anywhere by anyone. Here we discuss VPN limitations, explore VPN vs. ZTNA and provide a quick overview of how your organization can successfully move from VPN to ZTNA.

VPN Limitations

Introduced in the mid-1990s as a remote access solution, VPNs are well past their prime. Several U.S. government agencies, including the National Security Agency (NSA), have issued warnings about VPN limitations and potential vulnerabilities. They were never designed to be used with hybrid IT infrastructure or a globally dispersed workforce.

VPNs Are Inherently Insecure

One of the most serious VPN limitations centers around open ports. Without exception, every VPN concentrator has a presence on the internet with an open, continuously listening port. As a result, malicious actors can scan for and enter networks via these open ports, then move laterally to exploit targets.

TCP/IP authentication used by VPNs is another area of weakness. Most VPNs base “trusted” access on the user’s IP address and password. And time after time, threat actors easily manipulate this legacy approach to authentication. Valid login credentials are easy to acquire via social engineering, phishing, smishing, brute force attacks... the list goes on. Even two-factor authentication verification codes are easily captured. There are millions of stolen login credentials on the dark web for sale to the highest bidder.

VPNs Cause Architecture Complexity Issues

Many times, VPN administrators are forced to make a choice: create open policies for broad network access or create restrictive policies for limited network access. Restrictive policies are complex, error-prone and hard to manage given how quickly business requirements change (e.g., agility and digital transformation), so most choose broad access policies, which increases their organization's security risk.

This is further exacerbated by increased distributed workforces and dynamic IP creation inherent with cloud workloads. Beyond that, VPNs are hardware-bound, siloed solutions. This makes it cumbersome and costly to scale and inhibits your ability to automate processes and integrate with other solutions. Ultimately, VPNs are for remote access only ... and they can’t even do that securely.


It wouldn’t be fair to suggest a migration without exploring some of the main differences between VPN and Zero Trust Network Access (ZTNA).

ZTNA enforces the “principle of least privilege” for network access, which is now a leading industry mandate. ZTNA is architected to face today’s IT realities (vs. those of the 1990s) and offers significant benefits over outdated VPN structure. It’s like comparing the steam engine to the combustion engine. One served its time, while the other reigns supreme because it is adeptly designed for modern applications.

Hardware-bound VPNs remain static, while robust ZTNA solutions deliver the flexibility and scalability demanded by today’s businesses.

VPN vs. ZTNA: ZTNA offers several key benefits over VPN

  • Attack surface reduction: While VPN open ports are easily exploited, ZTNA architecture uses single packet authorization (SPA) to render resources invisible unless the user is authenticated or deemed a trusted identity.
  • Identity-centric authentication: ZTNA uses IP addresses as authentication criteria but goes much further to verify identity. It combines information from the identity store and layers on contextual variables such as time, date, location and device security posture.
  • Least privilege access: Users and machines are granted trusted but limited access only to resources needed to do their jobs. And with SPA technology and fine-grained microsegmentation, threat actors and infected devices can’t move across the network.
  • Programmable APIs: Unlike siloed VPNs, ZTNA solutions integrate business, IT and security systems for better network visibility and automation capabilities. ZTNA's software-defined nature ensures seamless and simultaneous scaling with dynamic infrastructures.

Move Beyond VPN Limitations With ZTNA

There are many VPN limitations that ultimately leave your organization vulnerable. When you decide it’s time for a change, follow these five steps to ensure a successful migration to Zero Trust Network Access:

  1. Understand your VPN landscape to build a baseline that considers all the technical, organizational and financial influences that may come into play during the migration process.
  2. Develop your ZTNA roadmap to set clear goals about where you want to start and end with ZTNA. Many more use cases beyond remote access can be supported by ZTNA, so prioritization should support the objectives, risks and desired security posture of your organization.
  3. Get started by selecting a ZTNA vendor then make decisions on infrastructure setup, policy creation, user onboarding and automation.
  4. Implement your first use case based on your roadmap and organizational goals.
  5. Scale up ZTNA implementation after the first successful use case until your entire organization is no longer constrained by VPN limitations.

Want to learn more? Download the 5-Step Guide to Implement VPN to ZTNA Migration.

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