What is Secure Access Service Edge (SASE) and How Does it Work?

Secure Access Service Edge (SASE) is a modern approach that combines wide area networking with cloud‑delivered security to provide secure, reliable access to applications and data from any location.

As organisations adopt hybrid work and cloud services, SASE helps maintain consistent security and user experience without relying on traditional, data centre‑centric designs.

CyberLab explains what SASE is, the core components, how it differs from Security Service Edge (SSE), and when to prioritise each.

SASE (pronounced “sassi” or “sassy”) converges SD‑WAN capabilities with cloud‑based security controls. Instead of routing all traffic through a central data centre, SASE enforces security as close as possible to the user, device or branch, and then connects to applications wherever they live, whether in public cloud, private data centres or SaaS.

At its core, SASE:

• Uses identity as the primary control point. Policies follow the user, device and context, not an IP address or fixed location.
• Delivers networking and security as a service, so controls are consistent and scalable.
• Improves user experience by steering traffic intelligently and enforcing security without unnecessary backhaul.

SASE brings together several building blocks. Individual features may already exist in many environments; SASE unifies them with a single policy and delivery model.

1) Software‑defined Wide Area Network (SD‑WAN)

SD‑WAN uses software to route traffic over multiple links such as MPLS, broadband and LTE. It prioritises important applications, improves resilience and reduces reliance on costly private circuits. Policies decide the best path based on performance, availability and business need.

2) Cloud Access Security Broker (CASB)

A CASB sits between users and cloud services to apply enterprise security policies. Typical functions include authentication, authorisation, data loss prevention, encryption or tokenisation, device posture checks, logging and threat detection for SaaS usage.

3) Firewall as a Service (FWaaS)

FWaaS delivers next‑generation firewall capabilities from the cloud. Instead of running and scaling on‑premises appliances, traffic is inspected in the provider’s fabric using a consistent rule set for all locations and users.

4) Zero Trust Network Access (ZTNA)

ZTNA replaces broad network access with explicit, least‑privilege access to specific applications. Every request is authenticated and authorised based on identity, device health and context. The principle is simple: never trust, always verify.

5) Secure Web Gateway (SWG)

An SWG protects users when accessing the web. It filters malicious content, enforces acceptable use policies, applies DNS and URL controls, and inspects traffic for threats and data exfiltration.

Security Service Edge (SSE) focuses on the security stack of SASE without the SD‑WAN element. SSE typically includes ZTNA, CASB, SWG and FWaaS delivered from the cloud. It is often the fastest path to modernise security for a distributed workforce when the underlying WAN is not being replaced.

• Choose SSE when the priority is to standardise and uplift security controls for remote users, branches and cloud access, while keeping the existing WAN in place.
• Choose SASE when you also want to modernise the WAN, consolidate providers and policies, and optimise performance end to end.

1. User or device connects from any location.
2. Traffic is steered to the nearest point of presence for policy enforcement.
3. Identity, device posture and context are evaluated.
4. Security controls are applied: ZTNA for private apps, SWG and CASB for web and SaaS, FWaaS for general traffic.
5. SD‑WAN selects the optimal path, delivering consistent performance and security.

This model removes unnecessary backhaul, improves visibility and simplifies operations with one policy plane.

1. Consistent security everywhere: The same policies apply to users in the office, at home or on the move.
2. Identity‑centric control: Policies follow users and devices, improving auditability and incident response.
3. Better user experience: Local breakout and smart routing reduce latency and improve SaaS performance.
4. Operational simplicity: Fewer point products, centralised policy and unified monitoring.
5. Scalability and agility: Capacity and features scale as a service, not by installing new hardware.
6. Stronger zero trust posture: Minimise implicit trust and reduce lateral movement.

1. Map use cases and traffic flows
   Identify who needs access to what, from where and on which devices. Prioritise high‑value applications and sensitive data.
2. Establish identity and device health as gates
   Integrate identity providers and device management so that policy decisions consider user role and device posture.
3. Start with SSE for quick wins
   Deploy ZTNA for private apps, SWG and CASB for web and SaaS, and FWaaS for consistent inspection. This can coexist with your current WAN.
4. Plan SD‑WAN evolution
   When ready, add SD‑WAN to consolidate connectivity, improve performance and complete the SASE model.
5. Consolidate vendors and policies
   Aim to reduce overlap and complexity. Fewer consoles and a single policy model make operations more effective.
6. Measure and iterate
   Track user experience, incident rates and policy coverage. Use findings to refine posture and roadmap.

1. Treating SASE as a product rather than an architecture and operating model.
2. Lifting and shifting legacy allow‑all access instead of enforcing least privilege.
3. Ignoring identity and device posture in policy decisions.
4. Running overlapping tools without a plan to consolidate, which increases cost and weakens visibility.
5. Neglecting change management and training, which are essential for adoption.

CyberLab helps organisations assess where SASE or SSE fits, design a pragmatic roadmap and implement the right controls at the right pace. If your team would like to explore options or validate your direction, we are available for a free initial consultation to discuss goals, constraints and next steps.

We help organisations work securely from anywhere, with security that is consistent, proportionate and easy to manage.