VPN vs. ZTNA vs. SDP vs. NAC: What’s the difference?

Updated 1/23/2023

You’re certainly familiar with the ins and outs of virtual private network (VPN) and network access control (NAC) solutions. Software-defined perimeter (SDP) and Zero Trust Network Access (ZTNA) are newer industry terms that you also likely know about but might not yet use to augment or replace older technology in your network security stack.

One thing’s for sure: if you want comprehensive, adaptive secure network access, you need to understand what each of these network security solutions is capable of and where they differ. Some have served their purpose and are headed for the sunset. Others are modern options designed to handle the evolving threat landscape and meet the “now and next” scalable secure access needs of complex and dispersed hybrid IT ecosystems.

Here we demystify the most common secure access options to help you make a more informed decision about where to take your network security strategy.

What is a Virtual Private Network (VPN)? Popular, but not secure enough

VPNs have been a network security staple for more than 25 years and in the “old world” of defined perimeters and physical offices, they sufficed. But they weren’t built to protect hybrid enterprise environments and workforce sprawl and now come with significant performance and security flaws that create vulnerabilities. Even the National Security Agency (NSA) has previously warned about VPN limitations and potential vulnerabilities.

Virtual private networks can only scale with more hardware (physical or virtual), which means a major investment of capital and time. And they’re famously temperamental, with connectivity and latency issues that throttle productivity. Additional VPN limitations include:

• Exposed ports: VPNs can be easily found and queried to discover the manufacturer and version, paving the way for threat actors to get in using common hacking tools
• Over-privileged access: VPNs are dependent on overly complex rules to prevent lateral movement
• Limited throughput: a typical VPN maxes out below 1Gbps which adds extra cost and complexity
• Vulnerable to man-in-the-middle attacks: VPNs don’t validate certificates on both sides of the communication path
• Centralized architecture: users coming into a central VPN access point are routed to the ultimate destination on the backend over some type of wide area network (WAN) … a topology that adds latency, causes performance issues, frustrates users and creates complicated routing dependencies
• Lack dynamic scale: VPNs must be architected to handle a certain volume of remote users and can’t dynamically scale up or down to handle unforeseen user fluctuations

What is Network Access Control (NAC)? It only addresses part of the issue

Like VPNs, network access control solutions are antiquated technology designed for a time when most people were in the office. They restrict access to endpoint devices that adhere to a defined security policy and perform authentication and authorization before granting access. However, NAC solutions also fall short: they can’t segment a network and can only protect on-premises devices … and that means they only offer a partial solution.

While providing a barrier to entry, NAC solutions are ineffective when it comes to protecting an environment once user access is granted. Over the years, NAC technology has become less effective and therefore isn’t seen as a long-term solution to secure your network access. Ultimately, network access control flounders for several reasons:

• Can’t provide fine-grained least privilege access and rely on existing network segmentation or VLANs (Virtual LAN)
• Have limited ability to make access decisions based on user context
• Don’t provide secure, encrypted communications between clients and services
• Must be used with another solution (such as a VPN) for remote users, which adds more cost, complexity and administration
• Aren’t practical to manage or scale due to the IT administration required to add devices and firewall rules for networks with large amounts of diverse users and devices that constantly change
• Don’t enable cloud security

What is Software-Defined Perimeter (SDP)? A more secure alternative

After decades of use, VPNs and NACs have taught some lessons and paved the road for a new, more secure way of granting access to networks.

Using Zero Trust principles—meaning no user or device is trusted until authenticated and no resources are visible unless access is granted—software-defined perimeter creates one-to-one connections between users and the resources they need—and only the resources they need—to do their work. And as the name implies, SDP is a software-defined solution rather than a hardware solution, making it very flexible and scalable for multifaceted hybrid IT environments.

SDP solutions were created to enforce the principle of least privilege, which reduces the attack surface by making all resources invisible unless a user is authorized and authenticated. A software-defined perimeter also surveys the environment and creates entitlements and the appropriate access level for each user in near real-time and continuously re-evaluates operational context, not just at the initial request.

What is Zero Trust Network Access (ZTNA)? Refining the software-defined perimeter

Zero Trust Network Access, the newest network security industry term, is now used interchangeably with software-defined perimeter to distinguish the more secure “authenticate first, connect second” principle of least privilege.

ZTNA is the most effective secure access method available. In contrast to a “default allow” mode of VPNs, NAC and firewalls, ZTNA is based on Zero Trust security principles and takes a “default deny” approach to digital resources. ZTNA and SDP are built on three core pillars:

1. Identity-centric: designed around the user identity, not the IP address, and requires user authentication before granting network access
2. Zero Trust: applies the principle of least privilege to the network and users by using micro-segmentation to make unauthorized resources invisible
3. Cloud-centric: engineered to operate natively in the cloud and deliver scalable security

ZTNA is quickly becoming the standard for network access across the hybrid workplace for enterprise environments and workforces. In fact, according to Gartner, “by 2024, at least 40% of all remote access usage will be served predominantly by Zero Trust Network Access, up from less than 5% at the end of 2020.

And Zero Trust maturity is paying off, as stated in the Cost of a Data Breach Report 2021 by IBM Security and the Ponemon Institute. The average cost of a data breach was 35% lower ($1.76M) per breach for organizations “in the mature stage of Zero Trust deployment” compared to those without Zero Trust deployed.

Industry-leading ZTNA: Appgate SDP

Appgate SDP delivers industry-leading Zero Trust Network Access to anything from anywhere by anyone. It requires users to be authenticated across a range of identity-centric and context-based parameters, such as role, time, date, location and device posture, before allowing access to enterprise resources … which prevents unsanctioned lateral movement.

Working with your existing security ecosystem to enforce Zero Trust principles, Appgate SDP features a single policy decision point that controls access across your organization’s entire IT ecosystem. In addition, exceptional API integrations mean less rip and replace and more augment and optimize to strengthen and simplify access controls by putting existing systems and data to work.

Additional resources

Five Steps for Successful VPN to ZTNA Migration ebook

Forrester New Wave: Zero Trust Network Access, Q3 2021

Zero Trust Starts With Secure Access infographic

Demo Appgate SDP