The Differing Roles of CIAM and IAM in Zero Trust Implementations

The basic mantra of “never trust, always verify” demands that every request be authenticated and authorized before access is granted, regardless of where it comes from. NIST formalized the model in SP 800-207. It sounds straightforward, but anyone who implements zero trust in a real-world environment quickly finds that the controls get complicated.

In practice, zero trust deployments involve constant judgment calls, as security teams weigh stronger verification against the friction it adds for users. On the customer side, too much friction shows up quickly in the bottom line.

Employees on corporate devices can be held to strict policies and hardware-backed MFA. Customers can’t. If the hurdles feel like too much hassle, they’ll take their business elsewhere. That’s why zero trust has to be implemented differently for different groups of users. 

The Great Divide in Zero Trust 

There’s a massive difference between internal and external identities, and that requires them to be managed in different ways. Standard identity and access management, or IAM, generally applies to employees, contractors and partners. For customers, subscribers and other external users, companies need customer identity and access management, or CIAM. 

Contrasting CIAM vs. IAM reveals a lot of similarities between the two, and also many differences. Cybersecurity teams must still adhere to the “never trust, always verify” principle, but the way it’s executed varies based on the kind of user trying to access the network. 

When it comes to internal users, organizations can get away with a lot more friction than it’s possible to impose on customers, because their employees and partners don’t have a competitor one click away. But customers have options, and they want minimal friction, so they generally gravitate to whatever transaction experience is easiest.  

Verify Every Employee Request with IAM

CIAM and IAM must be implemented differently. With standard IAM, the most important considerations are security and control and that’s done by enforcing least-privilege access to ensure that each user only has permission to access the data and services they need to get their specific job done. By locking them out of resources that they don’t need to access, the network becomes more secure. 

IAM environments should be based on human resources-driven provisioning and deprovisioning, which means that access should be granted to resources in a systematic way when someone is hired. When their tenure at the company ends, that employee’s access should instantly be revoked across every system, because they no longer have any reason to be poking around.  

Organizations can use robust methods to restrict internal users’ access to only the systems they need. The main measures that should be employed include device-posture checks on managed endpoints and phishing-resistant MFA for every user. 

With IAM, the priority is to limit the possibilities for lateral movement across the network. That way, if an employee’s account is compromised, the blast radius of that breach will be limited to just a few systems and databases. Contractors’ and partners’ access should be similarly scoped and time-bound for only the duration of their work. 

Balance Security and User Experience with CIAM

Zero trust was originally framed around workforce access. Google’s BeyondCorp, one of the best-known early implementations of zero trust, was built to secure the company’s own employees. The same principles apply to external users, but the mechanisms are very different.

Companies can and should offer customers strong authentication methods like passkeys, since many take security seriously. But making passkeys mandatory would be a mistake, as it would lock out customers whose older devices can’t use passkeys, or who aren’t yet comfortable with the technology.

The objective with CIAM is to keep friction to a minimum, and this means security teams must rely on passive signals instead. This means using techniques such as behavioral telemetry, adaptive risk scoring and scoped access boundaries, so that authentication is only required when the situation demands it – such as when a user logs in with a new laptop for the first time, or tries to gain access from an unknown location. 

An additional challenge is the need to design CIAM architectures to handle unpredictable surges in user traffic and adhere to regulations such as Europe’s GDPR and California’s CCPA. 

Why Separation Matters

Running employees and customers through the same identity tenant and policy set is risky. Should an administrator be compromised, both populations would be exposed. 

Having a single tenant can also lead to confusion with access logic, complicated by the fact that customer lifecycle and access rules often pull in different directions. 

Organizations should implement separate tenants and distinct policies for each user group. That doesn’t mean they need different vendors, since many platforms now cover both. The industry increasingly recognizes that internal, external and machine identities should be part of a single program with separate controls and environments. 

Machine and AI Agent Identities

AI agents have added a new layer to an old problem. Organizations already had to manage APIs and service accounts, and now autonomous agents act on behalf of users too. 

Alongside employees and customers, these machine identities form a separate category, with management challenges of their own.

Each one is a potential entry point for attackers. Machine identities should rarely be granted long-term access. Instead, they need short-lived credentials scoped to the task at hand, which expire once the task is complete and can be revoked earlier if needed.

The Right Way to Enable CIAM and IAM 

Here’s how the controls compare across both approaches in a zero trust implementation:

The principles behind zero trust stay the same for employees, customers and machines. The difference is in how IAM and CIAM apply those principles: how much you can demand from each, and how much you have to infer instead. Get that balance right, and security stops being a trade-off against user experience and becomes an advantage that protects your organization and keeps customers coming back.