What should be used instead of the AWS AWSCloudTrail_ReadOnlyAccess managed policy for least privilege?

Use a customer-managed policy that grants only the CloudTrail read actions needed for review and auditing. Scope access to the trails and related resources the user must inspect. Read-only access is safer than full control, but it still reveals logging configuration and investigative detail, so avoid giving it broadly to routine users.

What to use for least-privilege CloudTrail review access

Replace the broad AWS managed policy with a customer-managed policy that grants only the CloudTrail read actions required for inspection and auditing. Keep the scope tight to the trails, event history, and related resources the reviewer actually needs. That preserves the read-only intent without handing out broader visibility than the job requires.

Customer-managed policies are the better fit because they let you define the exact read surface instead of inheriting every permission AWS bundled into a general-purpose managed policy. For CloudTrail, that usually means separating routine audit review from admin tasks such as trail changes, destination changes, or log delivery administration. The more clearly those duties are split, the easier it is to enforce least privilege without slowing investigations.

Think of the replacement policy as a role-specific review permission set, not a convenience permission. If a user only needs to confirm whether trails exist, inspect recent events, or verify logging configuration, the policy should reflect that smaller task boundary. If someone also needs to manage retention, destinations, or integration settings, that is a different access profile and should not be folded into the same read-only grant.

Why broad read-only still creates avoidable exposure

Read-only access is safer than full control, but it still exposes security-sensitive detail such as logging topology, trail configuration, and investigative evidence. That information can help an insider understand what is monitored, what is retained, and which actions may be visible in future investigations. A broad managed policy therefore creates more visibility than many routine users need.

Using a custom policy also helps avoid permission creep over time. Managed policies are convenient starting points, but they tend to be reused far beyond the original review scenario. Once that happens, teams often stop asking whether the holder really needs CloudTrail visibility at all, and the policy becomes a default entitlement instead of a deliberate one.

For a deeper IAM treatment of policy scope, trust relationships, and permission analysis, the AWS IAM Policies and Roles Guide is the most directly relevant internal reference. When the access question sits inside a larger identity and governance review, the IAM and IGA Basics guide helps frame why the policy should be tied to a named job function rather than issued as a shared default.

How to scope the replacement policy in practice

Start by identifying the exact CloudTrail tasks the role must perform, then grant only those read actions and only against the trails or accounts the reviewer is responsible for. If the job is audit review, the policy should be narrower than a security operations analyst’s policy, and much narrower than an administrator’s. If the person does not need to change anything, do not include write actions just because they might be useful later.

Use the same discipline for cross-account or multi-trail environments. If the reviewer only needs one environment, do not extend visibility to every account by convenience. If there is a separate break-glass or incident-response use case, keep that access isolated and time-bound rather than mixing it into the routine review policy.

That pattern aligns well with the Privileged Access Management Guide, because CloudTrail review can become privileged when it exposes incident evidence or sensitive operational telemetry. It also matches the Just-in-Time Access and Zero Standing Privilege Guide, since review access should be activated only when needed instead of left permanently assigned.

Risk and Threat Considerations

A broad read-only CloudTrail policy can still leak valuable operational intelligence, especially when it is granted to users who do not need to investigate incidents. The main risk is not just accidental overexposure, but also the way read access can reveal logging gaps, detection coverage, and historical activity that an attacker or insider could use to plan next steps.

Failure mechanism: A managed policy provides a larger read surface than the role requires, so users inherit visibility into trails, events, and configuration details that should have been restricted to a smaller audience. That weakens separation between routine viewers and privileged investigators.

Impact: Overexposed review access can aid reconnaissance, increase the blast radius of a compromised account, and make incident data visible to people who have no operational need for it. In regulated environments, it can also complicate audit expectations around least privilege and access justification.

Standards & Framework Alignment

This section maps relevant standards and security frameworks to the operational risks and controls described in this guidance.

NIST SP 800-53 Rev 5, CSA Cloud Controls Matrix and CIS Controls v8 set the technical controls, while ISO/IEC 27001:2022 defines the regulatory obligations.

Framework	Control / Reference	Relevance
NIST SP 800-53 Rev 5	AC-6 — Least Privilege	CloudTrail review access should be limited to the minimum actions needed.
	AC-3 — Access Enforcement	The answer depends on enforcing scope to only the trails and resources a user may inspect.
	AU-9 — Protection of Audit Information	CloudTrail data is audit evidence, so access to it needs tighter control.
Recommendation — Restrict CloudTrail review permissions to the minimum actions and resources required. Enforce resource-scoped access so reviewers can only inspect approved CloudTrail targets. Limit access to CloudTrail audit evidence to authorized reviewers only.
ISO/IEC 27001:2022	A.5.15 — Access control	The question is about replacing broad access with tighter, role-specific access.
	A.8.2 — Privileged access rights	CloudTrail visibility can be privileged because it exposes security telemetry and investigation detail.
Recommendation — Define and apply access rules that grant only the CloudTrail permissions needed. Review and restrict privileged CloudTrail access rights to named roles.
CSA Cloud Controls Matrix	IAM — Identity and Access Management	CloudTrail access scoping is an IAM control problem in cloud environments.
Recommendation — Use IAM controls to scope CloudTrail access by role and business need.
CIS Controls v8	CIS-6 — Access Control Management	The answer is about replacing an overly broad permission set with a narrower one.
Recommendation — Assign only the CloudTrail permissions needed and remove broad inherited access.

Practitioner Guidance

What to verify: Confirm which CloudTrail objects the role must inspect, then test the policy against those tasks only. If the reviewer cannot complete the job without additional permissions, expand the policy narrowly, do not revert to a broad managed policy.

Common mistake: Teams often treat “read-only” as automatically safe and then grant it too broadly. For CloudTrail, the decision is not read versus write, it is whether the reviewer should see the logging surface at all, and if so, how much of it.

Practitioner takeaway: The safest replacement is the smallest custom policy that still supports the specific review workflow, because least privilege is about reducing unnecessary visibility as much as reducing unnecessary modification rights.