The problem we don’t talk about enough

After sign‑in, most systems “trust” a session until the access token naturally expires—often 60 minutes. If that token is stolen, an attacker may enjoy up to an hour of unfettered access. Tightening token lifetimes helps a little but frustrates users and still leaves gaps. CAE changes the rules by reacting in seconds, not hours.

CAE at a glance

Continuous Access Evaluation (CAE) is a capability that allows apps and identity providers to continuously re-check whether a user’s session should still be valid, based on real-time signals. In simpler terms, even after a user logs in, the system doesn’t fully “set and forget” their authentication until the token expires. Instead, it keeps evaluating important events and conditions that might affect the user’s access rights.

Conceptually: The identity system monitors a variety of security signals and events, and if something important happens, it will invalidate the user’s token immediately. Key triggers that CAE responds to include:

• User risk signals: For example, detection of compromised credentials or a high-risk sign-in on the user’s account. This might indicate the user’s identity is no longer trustworthy.
• Policy changes: For instance, an administrator updates a Conditional Access policy or security requirement. The conditions for access might have just become stricter.
• Critical events: Significant account events like the user’s password being reset or their account being disabled. Such events typically mean the current sessions should not continue.

When any such triggering event occurs, CAE immediately invalidates the user’s current access token, regardless of its remaining lifetime. The next time the application tries to use that token (which could be almost instantly), it is prompted to re-authorize the session. In practice, the app will silently check in with the identity provider (e.g. Entra ID) and realize it must re-authenticate the user or refresh the token under the new conditions. This all happens behind the scenes in real time. To the end-user, it may simply appear as a quick re-login prompt (if their session is cut off), but not as frequently or predictably as traditional periodic re-auth. In summary, CAE ensures that a user’s access is continually governed by current security context – not just the context at login time.

How it actually works

Continuous Access Evaluation relies on cooperation between the identity provider and the client application to enforce these real-time decisions. The process involves three main components or steps:

1. Shared Signals via CAEP: CAE leverages the Continuous Access Evaluation Protocol (CAEP) to exchange risk signals and event notifications between the IdP (e.g. Microsoft Entra ID) and the application. This is a standardized channel for the identity provider to instantly tell applications about security-critical events (like “user’s token should no longer be trusted”). The app and the IdP are essentially in constant communication about the session’s security status.
2. Event-Driven Revocation: When a high-risk event is detected – for example, an admin marks a user account as compromised or disables the account – the IdP immediately sends a revocation signal to any integrated application relying on that user’s session. Upon receiving this signal, the application knows it must treat the user’s token as invalid and cut off the session right away. This push notification mechanism drastically shortens the response time. The app doesn’t have to wait to check things on its own schedule, it gets told as soon as something happens.
3. Token Introspection: In addition to receiving push signals, applications also perform periodic token validity checks (a process often called token introspection) with the IdP (e.g. Entra ID). This means at intervals, or during certain actions, the app asks “is this token still good?” Entra ID can then inform the app if the token was revoked due to some policy or event. This ensures that even if a signal was missed or in the absence of a specific push event, the app will catch up quickly and enforce any new rules. Together, the push notifications and periodic checking guarantee near-instant enforcement of security changes on active sessions.
4. By combining these mechanisms, CAE creates a feedback loop: the identity system continuously monitors conditions and informs apps of any change, and apps continuously verify the token’s status. The result is a system where access decisions are no longer tied to fixed timeouts, but to real-time security context. A user’s session lives on only as long as it meets all current policies and risk checks – truly living up to the principle of dynamic, continuous assessment.

What triggers a snap decision?

• Account disabled or password reset
• Risk spikes (compromised user/sign‑in risk)
• Location changes (e.g., sudden country/egress shift)
• Device falls out of compliance
• Conditional Access policy updates (e.g., new MFA requirement)

Imagine that you disable a departing contractor’s account at 10:00. Without CAE, their open browser tab might keep working until 10:59. With CAE, the tab loses access within seconds—no more “goodbye‑hour” for data exfiltration.

Combined Benefits of Security and User Experience

• Security: Attack windows shrink from hours to seconds.
• UX: Fewer gratuitous re‑prompts; challenges happen for cause, not by timer.
• Ops: The number of helpdesk tickets decreased because users were signed out universally and required to reauthenticate.

Getting ready

• Ensure CAE‑aware apps/clients where possible; plan fallbacks for those that aren’t.
• Keep Conditional Access policies strong (MFA, device compliance, location)—CAE enforces them in real time.
• Educate users that unexpected re‑prompts can be a good thing: it means the system is protecting them.

Quick Recap

Zero Trust’s “never trust, always verify” means trust is dynamic. CAE operationalizes that inside each session—verification doesn’t stop at login; it continues for the session’s life.

• Logins start trust; CAE maintains it.
• Events, not timers, govern access.
• Security rises while friction falls.

Stay tuned! The second part of this blog we will discuss some concepts around CAEP and SSE.