SASE vs. Zero Trust: Understanding Essential Differences

Why SASE and Zero Trust Matter

SASE and zero trust exist because of the shortcomings of traditional security and connectivity methods. In particular, those older strategies were not designed to provide secure connectivity between cloud-based apps and remote users.

The issue is mainly one of evolution and scale. Organizations used to operate with their workers mostly in the office, accessing applications and data in the office’s data center. It made sense here for connectivity and security to be provided in the data center, and for the few workers traveling or working elsewhere to use a VPN that routed their traffic to the data center.

Today, however, in the age of the cloud and remote work, more activity usually occurs outside the office than in. Users, data, devices, and applications can be anywhere. Trying to force-fit traditional methods of providing security and connectivity at the data center means backhauling traffic from around the world to centralized locations. Adhering to a network-centric architecture in this way increases cyber risk and adds latency, harming the user experience. 

As remote work and cloud adoption grow, SASE and zero trust are transforming the ways that organizations deliver security and connectivity across decentralized environments.

What Is Zero Trust?

Zero trust is an architecture based on a key premise: “never trust, always verify.” It extends no entity (i.e., user, workload, or connected device) trust by default—instead, it proxies traffic and continuously verifies any entity based on context and risk before allowing access.

Rather than connecting entities to a trusted network for access to IT resources, zero trust architecture connects entities directly to the resources, without extending network access to anyone or anything. In other words, it enforces highly granular microsegmentation. This zero communication is delivered as a service, at the edge, from a global, purpose-built cloud.

A zero trust architecture lets organizations overcome the risks of network-centric architectures to:

• Minimize the attack surface by eliminating public IP addresses and inbound connections
• Stop compromise by inspecting all traffic (even TLS/SSL) and enforcing real-time policy
• Prevent lateral threat movement on the network through direct-to-app connectivity
• Block data loss across any leakage channel, including web, SaaS, endpoint, and more

What Is SASE?

Secure access service edge (SASE) is a networking and security paradigm that combines software-defined wide area network (SD-WAN) functionality with security service edge (SSE) to create a consolidated platform of solutions:

• SD-WAN to connect global locations and dynamically route network traffic
• Secure web gateway (SWG) to filter and secure web traffic
• Zero trust network access (ZTNA) to secure access to private applications
• Cloud access security broker (CASB) to monitor and control SaaS usage
• Data loss prevention (DLP) to secure access to sensitive data
• Firewall as a service (FWaaS) to inspect other traffic and enforce threat prevention

Zero Trust and SASE: Similarities and Differences

Zero trust and SASE share goals like improving security, enhancing user experiences, and reducing complexity. Where they differ is in how they provide connectivity and mitigate risk. By disconnecting security and connectivity from network access, zero trust overcomes challenges tied to network-centric, perimeter-based architectures, which most SASE solutions still rely on.

This table breaks down a few of the key differences between zero trust and SASE:

SASE vs. Zero Trust: Two Critical Questions

We’ve discussed how SASE and zero trust overlap. Both aim to help organizations embrace facets of modern work, like remote work and cloud apps, more effectively. Both consolidate security and connectivity delivered at the edge. The key distinction between SASE and zero trust, however, lies in two questions:

1. Secure connectivity for what?
2. Secure connectivity to what?

Secure Connectivity for What?
SASE focuses mainly on securing access for workforces because it was initially built on three main solutions focused on securing users: SWG, CASB, and ZTNA. With those as the core of SASE, developments in the framework have remained user-centric.

Zero trust architecture, on the other hand, aims to secure access across an organization’s entire IT ecosystem. It can secure any entity across workforces (users, contractors, and B2B partners), clouds (workloads across different public clouds), and branches (including IoT/OT devices within them) as they access any destination. So, while zero trust can meet the demands of SASE, the opposite may not be true.

Secure Connectivity to What?
SASE generally connects users to the network for access to applications also connected to that network. While it may deliver this connectivity via SD-WAN, this still amounts to a network-centric architecture operating on the basis of trusted locations, which is at odds with zero trust.

Moreover, most SASE offerings’ SD-WAN solutions rely on firewalls at each location for security, which is also not in line with zero trust. Even ZTNA, nominally a “zero trust” solution, often works by connecting users to a routable network to extend access to private apps.

Most SASE offerings, despite their positioning as modern frameworks, inherit the shortcomings of traditional network-centric architectures:

• They expand the attack surface by exposing public IP addresses, which are vulnerable to discovery by cybercriminals and allow inbound network connections.
• They fail to stop compromise, relying on firewalls (as virtual or hardware appliances) that struggle to inspect and secure encrypted traffic due to scalability limitations.
• They permit lateral threat movement by granting users broad network access instead of limiting access to specific applications.
• They require complex inter-site routing as networks grow across workforces, branches, and clouds, creating administrative and management challenges.

In short, relying on traditional SD-WAN and other network-oriented tools as part of a SASE implementation conflicts with the zero trust principle of least-privileged, any-to-any access. Organizations that want to implement SASE that meets the demands of zero trust, they need a different form of SD-WAN: Zero Trust SD-WAN.

Zero Trust SD-WAN and Zero Trust SASE

Zero Trust SD-WAN is the critical connective tissue that enables a SASE implementation to align completely with zero trust architecture. It overcomes the network-oriented weaknesses of traditional SD-WAN and SASE by extending least-privileged access to users, devices, and workloads across branches, data centers, and clouds. And it provides direct connectivity to the requested resource, rather than the network where the resource resides.

Benefits of SASE and Zero Trust Together

Incorporating Zero Trust SD-WAN into a complete SASE framework achieves true zero trust SASE, delivering:

• Stronger security: Continuous verification and elimination of implicit trust reduce cyber risk across workforces, branches, and clouds.
• Superior productivity: Direct-to-cloud zero trust connectivity provides fast, secure access and seamless experiences for distributed users.
• Cost savings: Consolidating security and networking tools in a cloud native zero trust platform reduces complexity, technology costs, and overhead.

Build a Secure Future with Zscaler Zero Trust SASE

The AI-powered Zscaler SASE is built from the ground up for security, performance, and scalability. With 160+ global data centers processing 500+ billion transactions daily, and by peering with hundreds of partners across major internet exchanges worldwide, Zscaler delivers unrivaled zero trust everywhere.

• Cloud-first architecture: Consolidate and simplify IT to accelerate cloud adoption, enhance user experiences, and standardize across locations.
• Full inline TLS/SSL inspection: Deliver comprehensive threat protection and data loss prevention for 100% of traffic with an AI-powered proxy architecture.
• Performance optimization: Optimize traffic routing via global peering with leading application and service providers to ensure superior user experiences.
• Zero trust communications: Securely connect your workforces, branches, and clouds without implicit trust and without ever bringing entities onto your network.
• Zero attack surface: Make IP addresses and your network invisible to the internet and unauthorized users. Threat actors cannot attack what they cannot see.