What Is Zero Trust Security? A Guide for Financial Services and Healthcare

By Travis DeForge, Abacus · Published October 29, 2026 · Updated October 29, 2026

Short answer: Zero trust is a security framework built on the core principle of “never trust, always verify.” It asks that teams approach anyone and anything with distrust, including users, applications, connections, and devices already inside the network. With Zero Trust, every request to reach a resource is checked on its own, using context like identity, location, and device health, and access is granted for that session only. NIST defines the model in Special Publication 800-207, published in August 2020.

Before Zero Trust was introduced, older approaches made the assumption that the network had a very clear barrier between inside and outside the network, each requiring different approaches. It was thought that if, for example, a user was able to successfully get past the firewall, this process was validation enough, and they were seen as trusted. That assumption stopped holding once staff began working from anywhere, applications moved to the cloud, and attackers started logging in with valid stolen credentials rather than just brute force breaking in.

How does Zero Trust work?

Zero Trust works by moving from blanket permissions across the network once initial verification is completed to continuous verifications of requests. Every attempt to reach a resource is evaluated at the moment it happens. The system asks who is asking, what device they are on, whether that device is healthy, what they are trying to reach, what the location the request is coming from, and whether the request fits normal behavior are all taken into consideration.

NIST SP 800-207, a publication by the National Institute of Standards and Technology (NIST) titled Zero Trust Architecture, describes three logical components that carry out access decisions. The policy engine decides whether to allow, deny, or revoke access. The policy administrator carries the decision out by establishing or ending the session. The policy enforcement point sits in front of the resource and applies it.

Access is granted per session, not permanently. A person who signs in successfully at 9 a.m. is not trusted indefinitely. If their device falls out of compliance, or their behavior changes, the next request is evaluated against the new facts.

Nothing about this requires replacing the network. Zero Trust is an operating approach, not a product. It is usually assembled from identity, device management, and access tooling that an organization already partly owns.

What are the principles of Zero Trust?

NIST SP 800-207 sets out seven tenets. Together they describe an environment where no request is trusted because of where it came from, and where every access decision is made fresh. In plain terms, NIST says:

• Treat every data source and computing service as a resource.
• Secure all communication, whatever the network location.
• Grant access to each resource one session at a time.
• Decide access with dynamic policy, using the observable state of the identity, the application, and the asking device, plus behavioral and environmental signals.
• Monitor and measure the integrity and security posture of every owned and associated asset.
• Make all authentication and authorization dynamic and strictly enforced before access is allowed.
• Collect as much information as possible about the current state of assets, network, and communications, and use it to improve security posture.

Two of these carry most of the practical weight. Per-session access limits what a stolen account can reach. Continuous monitoring means trust granted earlier can be withdrawn.

One gap sits outside the tenets but shows up in most environments. Service accounts, API keys, and machine identities often outnumber staff accounts, and they tend to hold broad rights with no expiry date. They need the same governance as people.

Outside of the tenets outlined by NIST, a Zero Trust framework also prioritizes least privilege access. This means that users and workloads are granted only the minimum amount of access necessary to successfully complete their required task. Permissions are temporary and revoked once the required session ends. Additionally, Zero Trust positions controls built to mitigate the impact of a breach, with the assumption that one will happen. Security controls are designed to limit lateral movement and reduce the blast radius of an incident when a threat actor is in the environment.

How is Zero Trust different from traditional perimeter security?

Perimeter security decides trust once, at the boundary. Zero Trust decides trust continuously, at each endpoint or new login. The practical difference shows up after a breach: in a perimeter model, one set of stolen credentials often reaches many systems, while in a Zero Trust model each system re-checks the request, limiting lateral spread through several checks.

What is Zero Trust network access (ZTNA)?

Zero Trust network access is a remote access technology that augments a VPN, building Zero Trust principles into the private connections organizations use to securely join devices to the internet. Instead of trusting a device on the network, ZTNA brokers a connection to one specific application only after checking the identity and the device. The rest of the network stays invisible. ZTNA uses standards such as deny by default, strict verification, least-privilege access, and application hiding to apply the core Zero Trust principle, “never trust, always verify.”

The difference between a traditional VPN connection and ZTNA matters during an incident. A VPN session on a compromised laptop is a foothold inside the network. A ZTNA session limits reach to the one approved application and nothing else. This limits a threat actor’s ability to scan or move laterally across a network when using a single compromised account.

ZTNA is one component of a Zero Trust strategy, not the whole model. It helps cover the access layer, but does not address data classification, non-human identities, or monitoring.

A benefit of ZTNA is that it does not change the employee experience. A VPN is a tool staff are used to connecting to. ZTNA is a mostly invisible layer added to a process people already expect when logging in for work. Staff open the application and the check happens behind it. This lack of friction tends to improve adoption, because the secure path is the easy path.

How do you implement Zero Trust?

Implementation runs in stages rather than as a project with an end date. CISA’s Zero Trust Maturity Model version 2.0, published in April 2023, gives a public roadmap for the work. It organizes the work into five pillars: Identity, Devices, Networks, Applications and Workloads, and Data.

Three capabilities cut across all five pillars: Visibility and Analytics, Automation and Orchestration, and Governance. CISA describes four maturity stages — Traditional, Initial, Advanced, and Optimal — which lets an organization identify its adherence level honestly rather than declaring itself “done” after a few foundational steps are taken.

Identity is almost always the right starting point. Identity access management like multi-factor authentication everywhere, a single directory, removal of standing admin rights, and an offboarding process that is meticulously followed are key. These steps deliver early risk reduction and are prerequisites for everything else.

Devices come next followed by applications, then data classification, which is the slowest pillar in almost every organization. Network microsegmentation is a common network security technique used to secure “east-west” traffic, or movement between servers or virtual machines within a network. Custom, workload specific security controls help ensure every connection within a network is verified and permitted.

When implementing Zero Trust, organizations should expect some “skeletons in the closet” that nobody wants to find. Unmanaged devices, shared accounts, service accounts with passwords set years ago, and applications that cannot support modern authentication are normal discoveries. Identifying critical assets and mapping how traffic moves across your infrastructure and who/what access what must happen.

The findings when locating sensitive data, applications, and assets are pivotal to improving an organization’s security posture. You can’t secure what you do not know you have. The inventory work is slow and exacting, but it is what makes every later decision and control effective and meaningful.

Sequence matters more than speed. Doing identity properly and then stopping for a quarter to accommodate other IT and security priorities is better than doing five pillars badly at once.

Finally, once the work is done, enforcement, monitoring, and maintenance have to be built into the team culture. Granular policies that deploy risk-based access controls and identity verification, and continuous logs, analyzation, and adjustment of those policies are a must.

Why do financial services and healthcare organizations need Zero Trust?

Both sectors hold data worth stealing, may have small internal IT teams relative to their risk, utilize third-party vendors, and face compliance standards that assume they can verify access within their environment. Zero trust addresses the attack patterns many threat actors use to access organizations in these industries, like using stolen valid credentials, attempting fraudulent MFA resets via a help desk, or using third-party vendors as an initial foothold.

For healthcare, the pressure is clinical as well as regulatory. Verizon’s 2026 Data Breach Investigations Report found that 54% of healthcare breaches involved the human element and 32% involved a third party. Shared clinical workstations, staff moving between sites, and large vendor chains can make validating access with traditional methods like location difficult.

Zero trust also supports HIPAA obligations directly. Access control, unique user identification, and audit controls are Security Rule requirements at 45 CFR 164.312. An architecture that logs every access request per resource helps produce that evidence as part of normal operation.

Consider what a stolen clinical login reaches today. In a flat network, it may reach the record system, the imaging server, the file shares, and the billing platform. Under Zero Trust it reaches only what that role is allowed, and only while the device stays healthy. The breach still happens, but the blast radius is smaller.

For financial services, Zero Trust can help firms around the globe meet shifting regulatory standards. One driver is the notification clock. The SEC’s Reg S-P, amended in 2024, requires covered firms to notify affected individuals no later than 30 days. Working out whose data was reached depends on per-resource access logs, which a Zero Trust model generates as a matter of course. Zero Trust also helps financial services firms satisfy the operational resilience and cybersecurity mandates of DORA, proving they can contain attacks and protect critical systems. In the UAE, the DIFC and ADGM both enforce strict rules requiring access controls like MFA and privileged access management, real-time monitoring, and secure data practices – all a part of a Zero Trust strategy.

In both financial services and healthcare, organizations are high value targets for cybercriminals due to the massive amounts of sensitive personal and transactional data they hold. Trust is also a core currency. A breach of client or patient data can not just cause an immediate financial loss or regulatory fine, but permanent reputational damage.

The wider threat data supports both cases. The same Verizon report found that 62% of breaches involved the human element. It also found that exploitation of vulnerabilities became the dominant initial access vector for the first time in 19 years, at 31% of breaches. Separately, IBM’s Cost of a Data Breach Report 2026 found the mean time to identify and contain a breach reached 247 days.

What goes wrong with Zero Trust projects?

The most common failure is buying a product and thinking the principles of Zero Trust have been satisfied. No single tool delivers the model. A product sold as “zero trust” usually covers one component, most often network access, while the remaining pillars stay untouched.

Five problems show up repeatedly:

Starting with the network instead of identity. Network segmentation is visible work, but an organization without consistent multi-factor authentication and clean identity data cannot make good access decisions anyway.

Ignoring non-human identities. Service accounts and API keys usually outnumber people and often hold broad, permanent rights. They are also the ones IT teams commonly forget to offboard.

Treating it as a project with an end date. Zero Trust is a maturity path. CISA’s Zero Trust Maturity Model, published in 2023, is staged precisely because the work is continuous.

Breaking clinical or trading workflows. Controls that fight how people actually work get routed around. In a clinical setting that can affect care, which is why workflow design has to be a part of the security design.

No plan for legacy systems. Imaging equipment, older clinical devices, and applications that cannot support modern authentication still exist. They need compensating controls and isolation, not denial.

The honest version is that most organizations will be part-way through implementing Zero Trust best practices for years. That is expected, and it is why a maturity model is more useful than a pass-fail audit.

About Abacus

Abacus is a managed IT and cybersecurity provider serving financial services firms and healthcare organizations globally since 2004. With in-house incident response specialists, a cyber R&D team, and a deep bench of GRC experts, Abacus supports more than 1,200 clients and 100,000 users, holding SOC 2 Type II attestation and CREST accreditation, with infrastructure and processes designed to support HIPAA and HITRUST compliance requirements.

Our experts provide security risk assessments that form the foundation of a proactive defense. We help you identify, analyze, and mitigate cybersecurity and regulatory risk through a structured approach that takes into account Zero Trust principles.

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