What is zero trust security?

Zero trust is a cybersecurity model that assumes every user, device, and application must be verified before accessing resources—whether inside or outside the organization’s network. In the zero trust framework, no access is inherently trusted; authentication and authorization are required for every interaction, and user behavior is continuously monitored to detect anomalies. 

Understanding what zero trust is can help MSPs better protect their clients as threats evolve. Adopting zero trust entails shifting from traditional perimeter-based security to a model built on the principle of “never trust, always verify.” Every access request is treated as a potential threat until proven otherwise, creating a virtual fortress that protects digital assets through proactive and adaptive security measures. 

Key takeaways 

• Zero trust eliminates implicit trust by continuously verifying every user, device, and application before granting access, regardless of network location. 

• Traditional perimeter-based "castle-and-moat" security relies on clear network boundaries that remote work, cloud services, and IoT devices are erasing, leaving modern distributed networks vulnerable. 

• Zero Trust Network Architecture (ZTNA) replaces outdated perimeter-based security with least-privilege access and context-aware authentication, preventing lateral movement by attackers. 

• MSPs should follow established framework standards like NIST 800-207 to maintain an effective zero trust architecture. 

• Modern cybersecurity solutions like multi-factor authentication (MFA), endpoint security, and continuous network monitoring provide the foundation for a zero trust framework. 

The principles behind zero trust 

At its core, zero trust security eliminates implicit trust and enforces strict verification for every access request. 

The traditional “castle-and-moat” IT security model assumes that once inside the network perimeter, users and devices can be trusted – a flaw that leaves systems vulnerable. If an attacker breaches this perimeter, they can move freely within the network. This approach relies on a secure outer boundary (the castle) with strict verification at entry points (the moat), but these defenses are no longer enough. 

Zero trust addresses modern threats by ensuring that no user or device is ever trusted by default or on an ongoing basis. It operates under the following principles: 

Least privilege access: Every entity is granted only the minimum permissions necessary to perform its tasks. Broad access rights are replaced with granular access rules based on user identity, device posture, location, and risk level. Only authorized entities can interact with specific resources, especially sensitive ones, minimizing exposure to unauthorized access. 

Continuous authentication: Unlike traditional models that authenticate users once per session, in zero trust models, verification is an ongoing process. Entities are continuously validated, and access can be revoked if unusual behavior is detected. 

Micro-segmentation strategies: Networks are divided into isolated segments, restricting lateral movement for attackers. This approach creates secure boundaries around individual applications, containing potential breaches and mitigating damage if a system is compromised. 

Multi-factor authentication (MFA): MFA requires users to verify their identity through multiple authentication factors. It enforces a combination of something users know (passwords), with something they have (security tokens or authenticator apps), or something they are (biometric data). The additional layers of authentication ensure that unauthorized access remains unlikely even when one factor is compromised. 

How zero trust works 

Zero Trust Network Architecture (ZTNA) is the practical implementation of zero trust principles, transforming traditional network access into an adaptive, context-aware system. Instead of relying on perimeter-based defenses, ZTNA enforces least-privilege access, granting users entry only to specific resources rather than entire subsets of data or complete networks. 

One example of this is NIST 800-207. This framework provides comprehensive guidelines for deploying zero trust architectures, detailing core components, security models, and use cases. All U.S. federal agencies must adhere to this framework. 

Zero trust networking security architectures rely on several key components: 

Network traffic monitoring: Continuous surveillance and analysis of network activity help detect anomalies and potential threats in real time. Detailed logs track access patterns and security incidents, enabling proactive policy enforcement based on observed behaviors. 

Identity verification mechanisms: Users must verify their identity through advanced authentication protocols such as MFA or behavioral analytics before accessing any resource. Together with continuous monitoring, this ensures that entities which may have gone rogue are prevented from accessing critical assets if suspicious behavior is detected. 

Contextual access decisions: Access permissions are adjusted dynamically based on factors like user role, location, device security, and past behavior patterns. Suspicious activity triggers additional authentication measures or restricted access to prevent potential breaches. 

Device trust validation: Each device is assessed for security compliance, including operating system integrity, patch levels, antivirus status, and adherence to security policies. Continuous health checks ensure that only trusted devices can access critical resources. This is particularly important for MSPs managing diverse client device ecosystems, to ensure high security standards are enforced consistently over time. 

Why zero trust is important 

The growing complexity of modern IT environments has rendered traditional perimeter-based or inheritance-based security obsolete. Unsecured BYODs, shadow IT, and unmanaged IoT devices pose a growing risk. Meanwhile, cloud services introduce countless new entry points, making the very concept of a network perimeter completely ineffective. 

High-profile incidents like the Ivanti breaches show how perimeter-based defenses like VPNs create massive blind spots that could be easily exploited by malicious actors. A single compromised account or device is sufficient to let an attacker move laterally until sensitive data is accessed. Once the “walls of the castle” are breached, there are few effective solutions to prevent widespread damage. 

For MSPs and their clients, the adoption of zero trust security is a necessary step to replace traditionally rigid and passive models with a flexible, proactive defense.  

• Micro-segmentation and least-privilege policies reduce attack surface, limiting the scope of potential breaches.  

• Identity verification and MFA ensures that only legitimate users and devices gain access to critical resources. 

• Even if an attacker compromises a system, continuous network monitoring and contextual access controls prevent unrestricted movement. 

Additionally, zero trust architectures strengthen compliance by aligning with regulatory frameworks like NIST, HIPAA, and GDPR to meet security requirements. Remote access can be enabled without compromising security, performance, and efficiency.  

Lastly, zero trust security also provides better visibility into network activity, allowing MSPs to monitor and control access patterns across their clients' environments more effectively.  

Zero trust use cases 

Zero trust security can help MSPs secure access to high-value enterprise assets in several ways. Here are some scenarios where ZTNA is especially impactful: 

Supply chain security: Third-party vendors and partners often need access to an organization’s systems, which can expose sensitive data and create security risks. Zero trust ensures that each entity is thoroughly authenticated and granted access only to the specific resources they need for their work. This prevents supply chain compromises from escalating into full-scale network breaches, as each connection is isolated and continuously monitored. 

Remote work security: Employees working remotely access corporate systems from various locations and devices, not all of which are sufficiently secure. Zero trust enforces identity verification, device trust validation, and contextual access controls to ensure secure remote access without relying on outdated strategies like VPNs. 

IoT device management: IoT devices are an ideal target for cyberattacks, as our 2025 MSP Threat Report explains. Many of them are manufactured with weak built-in security, and can be easily exploited as entry points into a network. Zero trust treats each connected device as potentially hostile, requiring continuous verification and operating under strict access limitations.  

Onboarding process for new employees, contractors, and third parties: Granting temporary or long-term access to new employees or external collaborators represents a security challenge. Zero trust frameworks allow MSPs to provision access rights precisely, ensuring new users receive only the permissions they need for their tasks, preventing excessive privileges.  

Zero trust best practices 

Enforcing zero trust requires a strategic, methodical approach. Best practices include: 

Never trust, always verify: The most basic principle of zero trust is that every connection attempt is potentially hostile, regardless of its source or previous trust status. Every access request must be verified and authorized and continuously monitored for suspicious behaviors. 

Apply least privilege organization-wide: Enforcing the principle of least privilege access requires careful mapping of user roles and responsibilities across the organization. Granular access policies should provide users with only the minimum permissions necessary for their tasks. These policies should be regularly reviewed and updated to reflect organizational changes. 

Network partitioning and micro-segmentation: Micro-segmentation strategies must be implemented to divide networks into secure zones based on data sensitivity, compliance requirements, and operational needs. This approach ensures that compromising one segment doesn't automatically grant access to others, effectively containing potential security incidents. 

Supporting zero trust with cybersecurity solutions 

Supporting a robust zero trust architecture requires adopting a combination of advanced technologies that enable continuous verification, strict access controls, and proactive threat detection. Modern cybersecurity solutions provide MSPs with the tools needed to establish and maintain zero trust security across their partners’ environments. 

• Multi-factor authentication (MFA) and identity management: The backbone of access control, these solutions enforce additional layers of identity verification, ensuring that only verified users can reach protected resources. 

• Endpoint security: Devices must be continuously checked for compliance, with security measures such as endpoint detection and response providing automated response to potential threats. 

• Network monitoring: Real-time traffic analysis provides visibility into all network traffic to detect anomalies and act proactively to prevent lateral movements. 

By implementing zero trust, MSPs can help clients build resilient, adaptive security frameworks that protect their networks against evolving cyber threats.  

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