AWS Backup Vault Lock | Deep Dive.

 

A deep dive into AWS Backup Vault Lock.

Scope:

•        How AWS Backup Vault Lock works,
•        Architecture, modes,
•        Compliance relevance,
•        Enforcement mechanisms,
•        Best practices, pitfalls,
•        Real-world design considerations.

Breakdown:

•        Core Purpose,
•        How It Works,
•        Vault Lock Modes,
•        Backup Vault Lock Lifecycle,
•        Architecture and Enforcement Flow,
•        Compliance Guarantee Mechanisms,
•        Threat Scenarios Vault Lock Addresses,
•        Scenarios Vault Lock Does NOT Protect,
•        Designing Retention Policies with Vault Lock,
•        Multi-Account Strategy,
•        Example Vault Lock Policy,
•        Monitoring and Audit,
•        Common Pitfalls & Warnings,
•        Recommended Best Practices,
•        Final thoughts.

 Intro:

•        AWS Backup Vault Lock is a WORM (Write-Once-Read-Many) immutability control applied to an AWS Backup vault, designed to prevent any user — including root — from altering or deleting protected backups within the lock retention window.
•        AWS Backup Vault Lock is used to enhance resilience against ransomware, insider threats, misconfigured IAM policies, or accidental deletions.

 1. Core Purpose

AWS Backup Vault Lock ensures that:

•         Backups cannot be deleted before their configured retention period.
•         Retention periods cannot be shortened once locked.
•         Policies that could permit deletion/modification cannot be modified in harmful ways.
•         Even AWS root users or accounts with full admin privileges cannot bypass or disable the lock.

It provides immutability guarantees required by:

•         SEC Rule 17a-4(f)
•         FINRA compliance requirements
•         CFTC regulations
•         Other regulatory bodies requiring tamper-proof storage

 2. How It Works

• Vault Lock is implemented as an additional enforcement layer within AWS Backup that overrides IAM permissions and Backup Vault Policy changes.

Key characteristics

Mechanism	Description
WORM enforcement	Backups cannot be modified or deleted until retention expires.
Policy freeze	Backup Vault Policies cannot be changed in ways that reduce protection.
Independence from IAM	Lock supersedes all IAM privileges.
Irreversible	Once moved into COMPLIANCE mode, it cannot be disabled or relaxed.
Cross-service protection	Applies immutability to backups from EBS, RDS, DynamoDB, EFS, EC2, Aurora, FSx, S3 (via AWS Backup), etc.

 3. Vault Lock Modes

AWS provides two distinct modes:

A. Governance Mode

•         Designed for testing and tuning backup policies before committing to full compliance.
•         Permits privileged IAM users with explicit permissions to:
•    Modify Vault Lock configurations
•    Reduce retention
•    Disable or remove lock
•         Still prevents casual or accidental changes.

Use case: QA, internal workloads, non-regulated data.

B. Compliance Mode

The highest immutability level.

Once enabled:

•         twtech cannot
•    Delete the vault
•    Shorten retention
•    Disable lock
•    Remove the lock period
•    Reduce WORM guarantees
•         Even root cannot override it.
•         Retention is guaranteed until it expires.

Use case: Regulated industries, ransomware defense, production-critical backups.

 4. Backup Vault Lock Lifecycle

Step 1 — Create a Vault

• twtech sets optional minimum and maximum retention.

Step 2 — Configure Vault Lock

• twtech enters Governance Mode first.

Step 3 — Validate Policies

• Ensure all backup plans match regulatory required retention.

Step 4 — Transition to Compliance Mode

• This action is irreversible.

Step 5 — Store Backups

• Backups created inside the vault are now immutable for the set period.

Step 6 — Expiration

After retention ends, AWS can automatically delete the backup.

 5. Architecture and Enforcement Flow

When a deletion attempt occurs:

1.     User sends a delete request.

2.     IAM policy allows or denies the request.

3.     Backup Vault Lock checks:

•    Is the resource retention expired?
•    Is the vault in governance or compliance mode?

4.     If Vault Lock prohibits deletion → request is rejected.

5.     AWS Backup logs the event into:

o   CloudTrail

o   Backup audit manager (if enabled)

NB:

Immutable retention enforcement occurs within the storage layer, not only at the application layer.

6. Compliance Guarantee Mechanisms

Vault Lock provides:

•         Hardware-level immutability (WORM at storage tier)
•         Irreversible governance policies
•         Retention enforcement independent of identity controls
•         Auditability and chained evidence via:
•    Backup Vault Events
•    Audit Manager Controls
•    CloudTrail Governance APIs

This meets the requirements for:

•         WORM record-keeping
•         Non-tamperable audit trails
•         Immutable retention enforcement

 7. Threat Scenarios Vault Lock Addresses

 Insider threat

• An admin attempting to delete incriminating or sensitive backups.

 Compromised admin credentials

• Ransomware actors deleting backups after gaining admin access.

 Misconfiguration

• A developer lowers retention accidentally.

 Regulatory requirement

• Auditors requiring evidence of retention enforcement.

 8. Scenarios Vault Lock Does NOT Protect

•         It does NOT prevent encryption key deletion (KMS key deletion can still destroy backup usability unless KMS key deletion protection is used).
•         It does NOT protect running workloads, only their backups.
•         It does NOT stop:
•    Data corruption in production systems
•    Bad configuration of backup plans
•    Incorrect resource exclusions

Use Backup Audit Manager to validate compliance.

 9. Designing Retention Policies with Vault Lock

Best practice layout:

1.     Primary Vault (non-immutable) for short-term backups

2.     Immutable Vault (Vault Lock Compliance Mode) for long-term archival

3.     Cross-account backup into a separate AWS Organization child account

4.     KMS key with key deletion protection

5.     Backup Plan with lifecycle:

•    Transition cold storage after 30–90 days
•    Retain for compliance period (e.g., 7 years)

 10. Multi-Account Strategy

A common design pattern:

Account Type	Purpose
Prod Account	Workloads + initial backup creation
Backup Account	Centralized immutable backup storage
Security Account	Audit & monitoring for backup access

NB:

• Cross-account copies are subject to Vault Lock immutability in the destination. This prevents deletion even if production is compromised.

 11. Example Vault Lock Policy

A policy that only permits backup copies and denies delete operations:

# json

{

  "Version": "2012-10-17",

  "Statement": [

    {

      "Sid": "DenyDelete",

      "Effect": "Deny",

      "Principal": "*",

      "Action": [

        "backup:DeleteBackupVault",

        "backup:DeleteBackupVaultAccessPolicy",

        "backup:DeleteRecoveryPoint"

      ],

      "Resource": "*"

    }

  ]

}

NB:

• When combined with Vault Lock, this becomes enforced immutability.

 12. Monitoring and Audit

Recommended tools:

CloudTrail Events

•         PutBackupVaultLockConfiguration
•         DeleteRecoveryPoint
•         UpdateBackupVault
•         CopyRecoveryPoint
•         PutBackupVaultAccessPolicy

Backup Audit Manager

•         Automatic evidence generation
•         Retention validation
•         Policy drift detection

CloudWatch Alarms

•         Detect deletion attempts
•         Unauthorized API calls
•         KMS anomalies

 13. Common Pitfalls & Warnings

❌    Enabling Compliance Mode too early

twtech might accidentally lock in wrong retention values and can't adjust.

❌    Assuming Vault Lock protects encryption keys

KMS keys require separate deletion protection.

❌    Storing backups in same account as workloads

Always use cross-account for ransomware defense.

❌    Reducing retention after Compliance Mode

Not possible — must wait for expiry.

 14. Recommended Best Practices

•         Use Compliance Mode for regulated/critical backups.
•         Use Governance Mode for testing.
•         Protect KMS keys with:
•    Key deletion window = 30 days (min)
•    Disable key deletion entirely if possible.
•         Set minimum retention at least:
•    7–35 days for ransomware protection
•    7 years for regulated workloads
•         Use Backup Vault Lock + Cross Account + KMS Hardened Keys
•         Turn on Backup Audit Manager

Final thoughts

•        AWS Backup Vault Lock is a critical mechanism for immutability, compliance, and ransomware resilience.
•        When AWS Backup Vault Lock properly integrated with cross-account backups, hardened KMS keys, and backup audit controls, it becomes a powerful and compliant long-term backup strategy that can withstand insider threats, breaches, and misconfigurations.