Amazon EventBridge Security | Overview.

Here’s twtech deep dive into Amazon EventBridge security.

Scope:

•         Key aspects of how AWS secures event ingestion,
•         Routing,
•         Delivery across accounts and services.

 1. Overview

•       Amazon EventBridge is a serverless event bus that connects application components using events from AWS services, integrated SaaS platforms, or custom sources.
•        Security in EventBridge centers around three major dimensions:
•         Authentication & Authorization (IAM)
•         Data Protection (in-transit and at-rest)
•         Cross-Account & Organizational Controls

 2. Authentication & Authorization

IAM Role and Policy Integration

EventBridge relies on AWS Identity and Access Management (IAM) to control who can:

• Create or modify event buses, rules, and targets.
• Publish (PutEvents) or consume (ReceiveMessage, Invoke) events.
• Manage schema registries and archives.

Example key IAM actions:

• events:PutEvents – publish events.
• events:PutRule, events:PutTargets – create rules and targets.
• events:DescribeRule, events:ListRules – inspect configuration.
• events:DeleteRule, events:RemoveTargets – cleanup and removal.

IAM policies define permissions at resource (event bus, rule, archive) and action levels, providing least privilege control.

3. Resource-Based Policies

EventBridge supports resource policies (like S3 or KMS) to enable cross-account or cross-organization access.

twtech can attach a policy directly to:

• Custom event buses
• Event archives
• Schema registries

These policies determine which AWS principals can:

• Publish events to the bus.
• Create or manage rules.
• Read archived events.

# Example use case:

Account A allows Account B to send events to its custom event bus via a resource policy.

 4. Event Flow Security

a. Event Sources

EventBridge validates the origin of each event:

• For AWS service events, identity is implicitly trusted via AWS internal authorization.
• For custom events or SaaS partners, EventBridge verifies IAM credentials or event source ARN trust.

b. Event Delivery

• When rules match events, targets (e.g., Lambda, Step Functions, SNS, SQS, API Gateway) are invoked using role-based access.
• Each rule references an IAM role that EventBridge assumes to deliver events safely to the target service.
• This model ensures delegated permissions — EventBridge only gets the rights explicitly granted to it.

 

5. Cross-Account & Organization-Wide Security

EventBridge supports:

• Cross-account event routing using event buses and resource policies.
• AWS Organizations integration – event buses can accept events only from specific accounts or an entire org, reducing risk of unauthorized event injection.

Organization-based condition keys:

• aws:PrincipalOrgID
• aws:PrincipalOrgPaths

These keys allow fine-grained restrictions such as: “Only allow events from accounts within Org ID X.”

 6. Encryption & Data Protection

a. Data in Transit

All communication to/from EventBridge is encrypted using TLS 1.2+.
This applies to:

• Event producers publishing events.
• Event targets receiving events.
• API calls through the AWS SDK or CLI.

b. Data at Rest

Events stored in EventBridge (temporary buffers, archives, and replay storage) are encrypted at rest using AWS KMS-managed keys:

• Default encryption with AWS-owned KMS keys.
• Optionally, you can configure customer-managed CMKs (SSE-KMS).

 7. Logging, Auditing & Monitoring

EventBridge integrates with AWS monitoring and audit services:

• CloudTrail: Logs all API activity (event bus creation, rule changes, event publishing).
• CloudWatch Metrics: Tracks delivery success/failure metrics.
• CloudWatch Logs: Can capture rule invocation logs for debugging.
• Event Replay: Useful for auditing past events or reprocessing after a policy change.

Common metrics:

• FailedInvocations
• ThrottledRules
• Invocations
• EventsPublished

 8. SaaS Partner Integrations

EventBridge supports verified SaaS partners through secure integration channels:

• Partners use a partner event source that requires a handshake (ARN binding) between AWS and the SaaS provider.
• Events are signed and scoped to a specific AWS account, ensuring authentic event delivery.

 9. Threat Mitigation & Best Practices

Category	Best Practice
Least Privilege	Grant only specific EventBridge actions (PutEvents, PutRule, PutTargets) to necessary roles.
Separation of Duties	Use different roles for publishing, managing rules, and consuming events.
Cross-Account Restrictions	Always define resource policies with specific principals or org IDs.
Encryption	Use customer-managed KMS keys for archives and replays.
Monitoring	Enable CloudTrail and CloudWatch alarms on EventBridge activity.
Validation	Implement event schema validation to prevent malformed or malicious payloads.

 10. Multi-Region & Availability Security

EventBridge is a regional service—events stay within the originating region unless twtech explicitly configure cross-region routing.

• Regional isolation limits blast radius of misconfigurations.
• Service operates on multi-AZ architecture with built-in redundancy and fault isolation.