Zero Trust security architecture: a practical guide for modern organisations

The NIST Zero Trust framework

The foundational reference for Zero Trust implementation is NIST Special Publication 800-207, published in August 2020. This framework defines seven core tenets: all data sources and computing services are considered resources; all communication is secured regardless of network location; access to individual enterprise resources is granted on a per-session basis; access is determined by dynamic policy including client identity, application, and the observable state of the requesting asset; the enterprise monitors and measures the integrity and security posture of all owned and associated assets; all resource authentication and authorisation are dynamic and strictly enforced before access is allowed; and the enterprise collects as much information as possible about the current state of assets and network infrastructure to improve its security posture.

At the core of the NIST model are three key components: subjects (users, devices, or services requesting access), resources (systems, data, or applications being accessed), and the policy enforcement and decision points that verify and authorise access. The Policy Decision Point (PDP) evaluates each access request against enterprise policy, while the Policy Enforcement Point (PEP) executes the decision by granting or denying access. This architecture ensures that every access request is evaluated individually based on identity, device posture, and contextual factors.

NIST SP 800-207A extends the framework specifically to cloud-native applications in multi-cloud environments, addressing the unique challenges of containerised workloads, service meshes, and ephemeral infrastructure. For organisations adopting cloud-first strategies, this extension provides critical guidance on securing dynamic, distributed environments.

Identity-centric security

Identity is the cornerstone of Zero Trust. In a world where the network perimeter is meaningless, identity becomes the primary security control plane. This means implementing robust Identity and Access Management (IAM) that goes beyond simple username and password authentication. Multi-factor authentication (MFA) is the baseline — not an option — and should be enforced for every user and every access point.

Conditional access policies add contextual intelligence to authentication decisions. These policies evaluate signals such as user location, device compliance status, sign-in risk level, and the sensitivity of the resource being accessed to determine whether to grant, deny, or require step-up authentication. For example, an employee accessing email from a managed device on the corporate network may proceed directly, while the same user accessing financial data from an unmanaged device abroad triggers additional verification.

Privileged Access Management (PAM) applies additional controls to high-risk accounts — system administrators, database administrators, and other users with elevated permissions. Just-in-time access provisioning, time-bound elevated permissions, and comprehensive session recording ensure that privileged access is tightly controlled and fully auditable. Identity governance — regular access reviews, role mining, and entitlement certification — ensures that access rights remain aligned with job responsibilities over time.

Micro-segmentation and network controls

Micro-segmentation replaces the broad trust zones of traditional network security with granular, workload-level access controls. Instead of a flat network where any compromised system can communicate with any other, micro-segmentation creates individual security zones around each workload, application, or data store. Lateral movement — the technique attackers use to move from an initial foothold to high-value targets — is dramatically constrained.

Implementation approaches range from network-based segmentation using software-defined networking (SDN) and next-generation firewalls to host-based micro-segmentation using agent software on individual workloads. The choice depends on the environment: network-based approaches work well for traditional data centres, while host-based solutions are better suited to dynamic cloud and container environments.

Zero Trust Network Access (ZTNA) has emerged as the modern replacement for traditional VPNs. According to Gartner, at least 70% of new remote access deployments will be served mainly by ZTNA instead of VPN services by 2025, up from less than 10% at the end of 2021. Unlike VPNs, which grant broad network access once authenticated, ZTNA provides application-specific access based on identity and context, dramatically reducing the attack surface. The ZTNA market was valued at USD 3.5 billion in 2024 and is growing at a CAGR of 23.2%.

Device trust and endpoint verification

Zero Trust extends verification beyond user identity to encompass the health and trustworthiness of the connecting device. A legitimate user on a compromised device is as dangerous as an attacker with stolen credentials. Device trust assessment should evaluate factors including operating system patch level, endpoint detection and response (EDR) agent status, disk encryption, firewall configuration, and whether the device is managed by the organisation.

Endpoint Detection and Response (EDR) and Extended Detection and Response (XDR) platforms provide continuous monitoring of device behaviour, detecting anomalies that may indicate compromise. Integration between EDR/XDR and the Zero Trust policy engine enables dynamic access decisions — for example, automatically revoking access if a device's risk score exceeds a threshold.

For organisations supporting bring-your-own-device (BYOD) policies, device trust presents unique challenges. Application-level controls, such as mobile application management (MAM) and data loss prevention (DLP) policies, can secure corporate data without requiring full device management. The key principle is that access privileges should be proportional to the level of trust that can be established for the device.

Implementation roadmap and common pitfalls

Zero Trust is a journey, not a destination. A practical implementation roadmap for SMEs should span 18-36 months and follow a phased approach. Phase one (months 1-6) focuses on foundational capabilities: comprehensive asset and data inventory, MFA deployment across all users, and initial identity governance. Phase two (months 7-18) introduces conditional access policies, initial micro-segmentation for critical assets, and ZTNA for remote access. Phase three (months 19-36) extends micro-segmentation, implements advanced analytics for continuous monitoring, and establishes automated response capabilities.

The most common pitfalls in Zero Trust implementation include treating it as a product rather than a strategy — no single vendor solution delivers complete Zero Trust. The biggest implementation challenges reported by organisations are lack of in-house expertise (47% of respondents) and insufficient budget (40%). Starting too broadly is another frequent mistake; successful implementations begin with a limited scope — protecting the most critical assets first — and expand incrementally.

User experience must remain a priority throughout implementation. Overly restrictive policies that frustrate legitimate users lead to shadow IT and workarounds that undermine security. The goal is security that is largely invisible to users when their behaviour and context are normal, while applying additional friction only when risk indicators are elevated. Regular communication with business stakeholders about what Zero Trust is (and is not) helps set appropriate expectations and build organisational support.

How Shady AS can help

At Shady AS SRL, we specialise in helping Brussels-based and European organisations design and implement practical Zero Trust security architectures tailored to their specific risk profiles and operational requirements. Our security consultants bring deep expertise across identity management, network architecture, endpoint security, and cloud security — the four pillars of a comprehensive Zero Trust programme.

Whether you are beginning your Zero Trust journey with a maturity assessment or ready to implement specific capabilities such as ZTNA, micro-segmentation, or conditional access policies, we provide the strategic planning and hands-on technical guidance to deliver results. Contact Shady AS SRL today to schedule a Zero Trust readiness assessment and take the first step toward a more resilient security posture.