Zero Trust Security
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What Is Zero Trust Security? Architecture, ZTNA & Vendors
Zero trust replaces the old idea that anything inside your network is automatically safe with a simpler rule: verify everything, every time, regardless of where the request comes from. Zero trust is a security model built on a single governing principle: never trust, always verify. No user, device, or network request should be trusted automatically, regardless of whether it originates inside or outside the traditional corporate network perimeter. The traditional model, often described as castle and moat, assumed that anything inside the network perimeter was safe by default. That assumption has collapsed under the weight of remote work, cloud adoption, and increasingly sophisticated supply chain attacks.
The CISA Zero Trust Maturity Model
CISA’s Zero Trust Maturity Model, most recently updated in 2023, defines a five stage progression across five pillars, giving organizations a structured way to assess current maturity and plan incremental investment.
- Identity Pillar
- Devices Pillar
- Networks Pillar
- Applications, Workloads & Data Pillars
Zero Trust Architecture and the NIST Framework
NIST Special Publication 800-207 is the most widely referenced formal definition of zero trust architecture, describing it as a set of principles rather than a single product: verify explicitly, use least privilege access, and assume breach. Zero trust is not something you buy as one product, it is an architecture that spans identity management, network access, device trust, and data access controls. Identity sits at the center of zero trust, with strong authentication combined with continuous validation of user context replacing the old assumption that a successful login alone proves trustworthiness. Microsegmentation divides a network into small, isolated zones so that even if an attacker compromises one segment, lateral movement to other systems is blocked by design.
Zero Trust vs VPN
Traditional VPNs grant broad network access once a user authenticates, effectively placing them inside the network perimeter with access to everything that perimeter contains. Zero Trust Network Access, or ZTNA, takes the opposite approach: it grants access only to specific applications a user is authorized for, never placing them on the broader network at all, and continuously re validates that access throughout the session. A compromised VPN credential can expose an entire network. A compromised ZTNA session, properly configured, exposes only the narrow set of applications that specific user was authorized to reach, which is the core security argument driving enterprise migration away from legacy VPN infrastructure.
Featured Zero Trust and ZTNA Vendors
Zscaler is the most widely deployed ZTNA platform globally, built as a cloud native service that replaces traditional VPN infrastructure entirely with identity aware, least privilege access. Cloudflare One combines ZTNA with Cloudflare’s existing global network and DDoS protection infrastructure. Palo Alto Networks Prisma Access integrates zero trust network access with Palo Alto’s broader SASE and firewall portfolio. Cisco Duo focuses heavily on the identity and device trust pillar specifically, providing strong multi factor authentication and device posture checking.
Implementing Zero Trust: Where to Start
Organizations rarely implement zero trust in one project. A practical sequence: start with strong multi factor authentication and identity governance, since identity is the foundation everything else builds on. Next, replace VPN based remote access with a ZTNA solution for your highest risk applications first. Then introduce microsegmentation incrementally, beginning with your most sensitive systems rather than attempting a full network redesign at once. Throughout, use a maturity model like CISA’s to track progress and justify the next phase of investment to leadership.
Zero trust is a security model built on the principle of never trust, always verify, requiring every user, device, and request to be authenticated and authorized continuously, regardless of whether it originates inside or outside the traditional network perimeter. It matters because the old assumption that anything inside the network is automatically safe no longer holds up against remote work, cloud adoption, and modern attack techniques.
A VPN grants broad network access once a user logs in, effectively placing them inside the network with access to everything it contains. Zero Trust Network Access grants access only to specific applications a user is authorized for, never placing them on the broader network, and continuously re validates that access throughout the session rather than only at initial login.
Most organizations start with strong multi factor authentication and identity governance as the foundation, then replace VPN based remote access with a ZTNA solution for high risk applications, followed by incremental microsegmentation beginning with the most sensitive systems. A maturity model, such as CISA's five stage framework, helps structure this as a phased program.
CISA's Zero Trust Maturity Model defines a five stage progression, from Traditional through Optimal, across five pillars: identity, devices, networks, applications and workloads, and data. It gives organizations a structured way to assess their current zero trust maturity and plan investment incrementally.
ZTNA, Zero Trust Network Access, is the specific technology that enforces zero trust principles for remote and application access. SASE, Secure Access Service Edge, is a broader architectural framework that bundles ZTNA together with other capabilities into a single cloud delivered platform. ZTNA is a component of SASE, not a competing alternative to it.
Yes, increasingly. Smaller organizations are common targets precisely because they often lack the defenses larger enterprises maintain. A practical starting point for a small business is strong multi factor authentication combined with a ZTNA solution for remote access.
Microsegmentation divides a network into small, isolated zones so that even if an attacker compromises one segment, they cannot move laterally to other systems without triggering additional authentication and authorization checks.
Zscaler is the most widely deployed ZTNA platform, built as a cloud native replacement for traditional VPN infrastructure. Cloudflare One and Palo Alto Networks Prisma Access are the next most commonly evaluated alternatives. Cisco Duo is frequently used specifically for the identity and device trust pillar alongside a separate ZTNA platform.