In today’s rapidly evolving digital landscape, the traditional concept of a secure network perimeter is becoming increasingly obsolete. As businesses move workloads to the cloud, adopt remote and hybrid work models, and deal with an ever-expanding attack surface, the need for a more modern, flexible, and robust security framework is clearer than ever.
For many organisations, Virtual Private Networks (VPNs) were once the go-to solution for remote access and perimeter defence. However, the rise of Secure Access Service Edge (SASE) presents a powerful evolution in network security, one that addresses the limitations of legacy systems and aligns better with the demands of today’s decentralised environments.
This blog explores the shift from VPNs to SASE, why it’s happening, and how businesses can build a modern security perimeter suited for 2025 and beyond.
The Legacy of VPNs: Useful but Outdated
VPNs have long served as a reliable method for creating encrypted tunnels between remote users and internal networks. They were effective when most employees worked from central offices and applications were hosted in on-premise data centres. But times have changed.
In today’s distributed IT environment:
- Applications are hosted across multiple clouds and SaaS platforms.
- Users connect from various devices and locations.
- The volume and sophistication of cyber threats have increased dramatically.
VPNs struggle to provide granular control, scale efficiently, or enforce consistent security policies across a distributed workforce. Moreover, once a user connects via VPN, they often gain broad network access, increasing the risk of lateral movement in case of credential compromise.
Introducing SASE: A Cloud-Native Approach to Security
Secure Access Service Edge (SASE), pronounced “sassy,” was coined by Gartner in 2019 as a new category that converges wide-area networking (WAN) and network security services into a single cloud-delivered model.
Core components of SASE include:
- Software-Defined WAN (SD-WAN): Intelligent routing and optimisation of traffic across cloud and on-premise environments.
- Cloud Access Security Broker (CASB): Enforces security policies for cloud services and SaaS applications.
- Zero Trust Network Access (ZTNA): Validates every user and device before granting access, based on context and identity.
- Firewall as a Service (FWaaS): Delivers scalable, centralised firewall capabilities from the cloud.
- Secure Web Gateway (SWG): Protects users from internet-based threats by inspecting and filtering traffic.
SASE allows organisations to apply security policies consistently, regardless of where users are located or where data resides.
VPN vs. SASE: Key Differences
Architecture
Traditional VPNs are built on hardware or software-based tunnelling systems that route traffic through central gateways. This model often becomes a bottleneck as businesses grow. In contrast, SASE is a cloud-native architecture that distributes security functions closer to users and applications, ensuring faster and more secure access regardless of location.
Scalability
VPN solutions tend to struggle with scalability. Adding users or locations requires more hardware, bandwidth, and manual configurations. SASE, however, is designed for scale. As a cloud-delivered model, it effortlessly accommodates growing workloads and a dispersed workforce without the need for infrastructure upgrades.
Security Model
VPNs operate on a perimeter-based security model—once a user is inside the network, they have broad access. This approach is risky in today’s threat landscape. SASE follows a Zero Trust model, enforcing strict identity verification and least-privilege access for every session, drastically reducing the risk of lateral movement and breaches.
Access Control
With VPNs, access is typically broad, allowing users into the entire network once connected. SASE offers granular, context-aware access control. It evaluates users based on identity, device posture, location, and more to grant precise access to specific applications or data.
Visibility and Control
VPNs provide limited insight into user activity and traffic patterns, making it harder to detect threats in real-time. SASE provides centralised visibility, logging, and analytics. It enables IT teams to monitor access, detect anomalies, and enforce policies consistently across the environment.
Maintenance and Management
Maintaining VPN infrastructure involves managing hardware, patches, and configurations—often leading to high operational costs and complexity. SASE simplifies management by delivering security and network services as a unified, cloud-based solution. Updates, policy enforcement, and scaling are handled centrally with minimal IT involvement.
Why Organisations Are Making the Shift
Organisations across the UK and globally are rapidly moving away from traditional Virtual Private Networks (VPNs) and adopting Secure Access Service Edge (SASE) solutions. This shift is driven by evolving business needs, technological advancement, and a changing cybersecurity landscape. Below are the key reasons behind this transformation:
Workforce Mobility
In a post-pandemic world, hybrid and remote work models have become the new norm. Employees now expect to access corporate resources from anywhere—home, co-working spaces, or while travelling. Traditional VPNs, which were originally designed for limited remote access, struggle to scale and often introduce latency and security concerns.
SASE is inherently built for this new environment. It delivers secure access via the cloud, ensuring that users—regardless of location or device—can connect securely and efficiently. It eliminates the need to route traffic through centralised data centres, thereby improving performance while maintaining a strong security perimeter.
Cloud-first Strategies
Modern organisations are embracing cloud-native applications and infrastructure to increase agility and innovation. However, VPNs were never intended to support the dynamic, distributed nature of cloud environments. Routing cloud traffic back to on-premises VPN concentrators not only creates bottlenecks but also increases exposure to potential security risks.
SASE supports cloud-first strategies by providing direct-to-cloud connectivity with built-in security. Whether users are accessing Microsoft 365, Salesforce, or AWS-hosted applications, SASE ensures traffic is optimally routed and protected without the overhead of legacy infrastructure.
Improved Security Posture
One of the primary drivers behind the shift to SASE is the need for a more robust and integrated security model. Unlike VPNs, which offer basic encryption and tunnelling, SASE brings together multiple security capabilities—including Secure Web Gateway (SWG), Cloud Access Security Broker (CASB), Zero Trust Network Access (ZTNA), and Firewall-as-a-Service (FWaaS)—into a single framework.
This convergence allows organisations to enforce identity-based access controls, detect threats in real time, prevent data exfiltration, and ensure compliance with regulatory requirements. SASE effectively reduces the attack surface while adapting to user behaviour and risk context.
Operational Efficiency
Managing a patchwork of point solutions—VPNs, firewalls, proxies, and security appliances—adds complexity for IT teams. It results in fragmented visibility, inconsistent policy enforcement, and increased administrative overhead.
SASE addresses these issues by centralising security management through a unified platform. This allows IT teams to apply consistent security policies across all users and devices, monitor network activity from a single dashboard, and automate threat detection and response workflows.
Cost-effectiveness
Consolidating multiple security and networking tools into a single cloud-based platform offers significant cost savings. Traditional VPNs often require expensive hardware upgrades, maintenance, and licensing for additional security features. SASE eliminates many of these costs by offering a subscription-based model and reducing the need for physical infrastructure.
Moreover, with fewer point solutions to manage, organisations can streamline operations, reduce training requirements, and reallocate IT resources to more strategic initiatives.
Building a Modern Security Perimeter: Steps to Take
Transitioning to a modern security perimeter with SASE isn’t just a technological upgrade—it’s a strategic transformation. Organisations must take deliberate steps to ensure a smooth migration and long-term success. Here’s a structured approach to begin the journey:
Assess Your Current Environment
Before implementing SASE, it’s crucial to understand the existing security and network architecture. Identify how employees and third parties access business-critical systems, whether those systems are on-premises, in the cloud, or hybrid. Evaluate current pain points with your VPN solution—such as scalability issues, latency, or gaps in visibility.
A thorough assessment helps identify risks, map out user behaviours, and prioritise the most critical areas for SASE deployment. It also creates a baseline against which future improvements can be measured.
Adopt a Zero Trust Mindset
Zero Trust is at the heart of modern security. Instead of assuming trust based on network location, Zero Trust operates on the principle of “never trust, always verify.” Implementing Zero Trust means ensuring that every access request is authenticated, authorised, and encrypted—regardless of where it originates.
This involves establishing least-privilege access controls, identity verification through multi-factor authentication (MFA), and continuous session monitoring. These capabilities are natively supported in SASE, allowing security policies to adapt dynamically based on context, risk, and user identity.
Choose the Right SASE Vendor
Not all SASE solutions are created equal. When selecting a provider, prioritise vendors that offer full SASE functionality—including ZTNA, SWG, CASB, FWaaS, and SD-WAN—in a single integrated platform. Ensure the vendor’s cloud infrastructure is reliable, scalable, and globally distributed to meet your performance needs.
Consider the vendor’s track record, customer support, threat intelligence capabilities, and integration with your existing tools (such as identity providers and endpoint detection systems). A trusted partner will play a vital role in successful deployment and long-term optimisation.
Plan a Gradual Transition
Switching from VPN to SASE doesn’t have to be a disruptive all-or-nothing move. A phased approach allows you to test configurations, train teams, and resolve unforeseen issues early. Start with a pilot programme involving a small group of remote users or specific departments.
Use the insights gained to fine-tune policies, gauge user experience, and validate security outcomes. Once proven, expand the deployment gradually across locations, devices, and user types. This approach reduces risk and ensures business continuity throughout the transition.
Train Your Teams
Technology alone cannot secure your organisation—people play a vital role. It’s essential to train both IT personnel and end-users on how to use SASE tools effectively and securely. For IT teams, this means understanding how to configure policies, monitor activity, and respond to incidents.
For end-users, training should cover how to authenticate securely, recognise phishing attempts, and report suspicious behaviour. By building a culture of security awareness, you can maximise the impact of your SASE investment.
Monitor and Optimise Continuously
Once your SASE solution is live, the work doesn’t stop there. Use real-time analytics and threat intelligence to monitor user behaviour, application performance, and policy effectiveness. Continuously review and refine access rules, particularly as users change roles, new applications are introduced, or the threat landscape evolves.
Automated policy enforcement, anomaly detection, and centralised reporting allow for proactive risk management. The more data your SASE solution ingests and analyses, the smarter and more responsive your security perimeter becomes.
Final Thoughts
The shift from VPNs to SASE isn’t just a technological upgrade—it’s a strategic move towards future-proofing your organisation’s cybersecurity. In a world where users are everywhere, applications are in the cloud, and threats are increasingly sophisticated, traditional perimeter defences are no longer enough.
By embracing a SASE model, businesses gain the agility, visibility, and security needed to thrive in the digital age. It’s not about replacing one tool with another; it’s about rethinking how we define and defend the modern perimeter.
