Implementing Zero Trust in Three Phases: Identity, Application Access, and Visibility

Zero Trust requires organizations to verify who is requesting access, evaluate the circumstances of that request, and grant only the permissions needed for the task. Being connected to the corporate network should not automatically establish trust.

A practical implementation can follow three phases:

1. Establish identity and credential boundaries.
2. Protect applications with identity-aware access.
3. Improve visibility, detection, and response.

These phases overlap. Logging should begin with the first deployment, while identity and application controls continue to improve as the organization learns from its telemetry.

Phase One: Identity Control and IAM Credential Boundaries

Identity is the foundation of Zero Trust. Before changing how users connect to applications, establish which identities exist, how they authenticate, and what they can access.

This includes employees, contractors, administrators, service accounts, applications, and automated agents.

1. Establish a reliable identity foundation

Inventory identity providers, directories, local accounts, and application-specific credentials. Identify:

• Accounts that remain active after employees or contractors leave.
• Privileged accounts without clear owners.
• Applications that bypass centralized authentication.
• Service accounts with excessive permissions.
• Credentials shared between people, applications, or environments.

Centralize authentication into as few identity providers as operationally necessary. This simplifies policy management, account revocation, and investigation.

Acquisitions, subsidiaries, and test environments may require multiple identity providers. In those cases, define clear federation relationships, account ownership, and consistent lifecycle controls.

The identity provider supplies authentication and identity attributes. Applications and policy enforcement services still need to make and enforce authorization decisions. Network analysis and visibility tools can correlate activity with identity information, but their network observations remain another source of evidence.

2. Enforce multifactor authentication

Require MFA for workforce access, with particular attention to administrators and users handling sensitive information. Prefer phishing-resistant authentication where supported.

Review the entire authentication lifecycle:

• Enrollment and device registration.
• Lost-device and account-recovery procedures.
• Help-desk identity verification.
• Emergency access.
• Session expiration and revocation.

A strong login policy can be undermined by a weak recovery process or an unmanaged exception.

3. Implement single sign-on

Single sign-on allows applications to rely on a centrally managed identity provider instead of maintaining separate passwords.

Its security value depends on consistent enforcement. Remove unnecessary local login paths, promptly disable departed users, and review application assignments and federation configuration.

SSO also concentrates responsibility in the identity platform. Protect identity administrators, monitor configuration changes, and maintain tested emergency-access procedures.

4. Define IAM boundaries

Authentication establishes identity. IAM determines what that identity is allowed to do.

Define permissions around actual responsibilities and separate:

• Production from development.
• Human access from workload access.
• Routine work from privileged administration.
• Application access from access to underlying data.

Review inherited permissions as well as direct grants. A narrowly scoped project role provides little protection if the same person holds broad permissions at a parent folder or organization.

For workloads, prefer managed identities and short-lived credentials where practical. Google Cloud Workload Identity Federation enables supported external workloads to access Google Cloud without relying on service account keys. docs.cloud.google.com

5. Automate approved privilege elevation

Move toward temporary, task-specific access rather than permanently assigned administrative permissions.

A practical process should require a requester to specify the task, resource, justification, and duration. Approval should follow policy, access should expire automatically, and the resulting activity should be auditable.

Google Cloud Privileged Access Manager supports just-in-time, time-bound privilege elevation, with approval workflows and auditability. It is a separate capability from Access Context Manager. docs.cloud.google.com

Where GCP Access Context Manager fits

Access Context Manager defines contextual access requirements through access policies and access levels. Depending on the integration, those requirements can incorporate attributes such as identity, device posture, or network origin.

ACM defines context; it does not independently enforce access or replace IAM. Services such as Identity-Aware Proxy and VPC Service Controls consume relevant policies and enforce them within their supported scope. docs.cloud.google.com

The components answer different questions:

A proposed access policy might require an authorized administrator to use a managed device and obtain temporary privileges before performing a production change. Each part must be implemented through the appropriate supported control.

Phase-one outcome: identities have owners, credentials have boundaries, and privileged access follows a controlled lifecycle.

Phase Two: Deploy Zero Trust Access in Front of Applications

The next phase changes the access model from broad network connectivity to access to specific applications.

1. Introduce ZTNA for suitable applications

Traditional VPN connections can provide access to a substantial portion of an internal network. Zero Trust Network Access can restrict users to the applications they are authorized to use.

Start with applications that have clear owners, identifiable user groups, and supported authentication patterns. Pilot the controls before expanding them.

Google Cloud Identity-Aware Proxy provides identity-aware access for supported applications and administrative connections. It evaluates authentication and relevant IAM authorization, with context-aware controls available for supported configurations. docs.cloud.google.com

VPN replacement should follow application requirements. Some legacy protocols and operational dependencies may require a transitional approach.

2. Federate access and evaluate attributes

Use federation to connect applications to the identity provider. Define access using relevant attributes, such as:

• Role and group membership.
• Employment or contractor status.
• Device compliance.
• Resource sensitivity.
• Approved access duration.

Ensure those attributes come from governed sources and remain current. Incorrect group membership or stale contractor status can produce incorrect access decisions.

Keep authorization inside the application as well. Passing an access proxy should not automatically permit every action or expose every customer record.

3. Integrate threat and device signals

Where supported, incorporate endpoint posture and identity-risk signals into access decisions.

For example, a privileged user signing in from a newly registered device might need additional verification. A device identified as compromised might lose access to sensitive applications.

Specify what happens when signals are unavailable, how quickly changes take effect, and who can resolve legitimate access failures. Test these behaviors rather than assuming every integration continuously reevaluates every session.

4. Prevent bypass of the access layer

A protected application can remain exposed if users can reach its backend through another address, route, or login path.

Review direct backend access, alternate endpoints, service-to-service connections, and administrative interfaces. Secure the path from the access gateway to the application, and validate trusted identity information at the appropriate boundary.

ZTNA complements application authorization, network segmentation, and workload security.

Phase-two outcome: application access depends on identity, permissions, and relevant context, with bypass paths addressed.

Phase Three: Improve Visibility, Centralize Logs, and Detect Unsafe Activity

Access controls need observable evidence. The organization should be able to determine who accessed a resource, why access was permitted, what happened afterward, and whether intervention is necessary.

1. Define the visibility questions

Begin with the questions investigators and operators need to answer:

• Who accessed a sensitive application?
• Was the device compliant?
• Who changed an IAM policy?
• Which service account accessed production data?
• Was temporary access approved and subsequently removed?
• Did traffic reach an unexpected destination?

Use those questions to select telemetry and identify gaps.

2. Centralize relevant logs

Collect identity, application, endpoint, cloud audit, access-proxy, and network telemetry into a governed logging environment.

In Google Cloud, verify audit coverage explicitly. Most Data Access audit logs are disabled by default, with exceptions such as BigQuery, so default logging should not be assumed to capture every sensitive data operation. docs.cloud.google.com

Protect the logging environment itself. Restrict deletion and configuration changes, define retention, and monitor ingestion failures. Avoid unnecessarily recording credentials, tokens, or sensitive application content.

3. Turn telemetry into actionable monitoring

Prioritize detections connected to meaningful risks:

• Unexpected privilege grants.
• Service account key creation.
• Access by disabled or departed users.
• Unusual sensitive-data access.
• Repeated access denials.
• Attempts to bypass the application gateway.
• Unexpected outbound communication.

Every important alert needs an owner and a response procedure. Test whether the team can revoke access, isolate a device, disable a credential, and preserve evidence.

4. Detect unencrypted network traffic

Identify cleartext communication involving sensitive data or credentials. Review both user-facing connections and internal service-to-service traffic, including connections behind TLS-terminating proxies.

VPC Flow Logs help identify communication patterns, endpoints, ports, and traffic volumes. However, they use sampling and aggregation rather than providing a complete packet capture. docs.cloud.google.com

Port numbers alone do not prove encryption. A connection on port 443 does not establish that TLS is correctly configured, and another port does not necessarily indicate cleartext traffic.

Validate encryption using a combination of configuration reviews, TLS testing, application or proxy telemetry, and appropriately authorized packet inspection where necessary. Review certificate validation and backend encryption as well as the public endpoint.

Phase-three outcome: access decisions and subsequent activity can be investigated, suspicious behavior triggers a response, and encryption gaps are identified through evidence.

Measure Progress Across All Three Phases

Zero Trust becomes an operating discipline when identity, application access, and monitoring work together. The organization can then demonstrate how access is granted, how misuse is detected, and how authority is withdrawn when circumstances change.