c2.3 Protect training-data integrity with S3 Object Lock and versioning

Make training data tamper-evident and recoverable

If an attacker (or a mistake) alters your training set, a model fine-tuned on it inherits the damage — data poisoning is hard to detect after the fact. Two S3 features make the dataset defensible:

• Versioning keeps every version of an object, so an overwrite or delete never destroys the original — you can roll back to a known-good version.
• Object Lock enforces write-once-read-many (WORM): a locked object version cannot be overwritten or deleted until its retention period expires.

Object Lock only works on a versioned bucket, and versioning is enabled automatically when you enable Object Lock.

Enable versioning, then a default retention

Turn on versioning and set a default Object Lock retention so new training objects are protected automatically:

# Versioning first (Object Lock requires it)
aws s3api put-bucket-versioning \
  --bucket my-bedrock-training-data \
  --versioning-configuration Status=Enabled

# Default WORM retention: 30 days in GOVERNANCE mode
aws s3api put-object-lock-configuration \
  --bucket my-bedrock-training-data \
  --object-lock-configuration '{
    "ObjectLockEnabled": "Enabled",
    "Rule": { "DefaultRetention": { "Mode": "GOVERNANCE", "Days": 30 } }
  }'

Choose the right retention mode

• GOVERNANCE — objects are protected, but users with the s3:BypassGovernanceRetention permission can still remove the lock. Good default for tamper-evidence without locking yourself out.
• COMPLIANCE — no one, not even the root account, can shorten the retention or delete the version until it expires. Use only when you are certain about the retention period, since it cannot be undone.

DefaultRetention accepts either Days or Years — not both.

Pair it with integrity checks

WORM protects against tampering after upload; also record a checksum (e.g. an S3 checksum or a manifest hash) when you ingest a dataset, so you can prove the exact bytes a given model version was trained on. Combine with the customization CMK control so the protected data is also encrypted under your key.

Naming note: replace the bucket name and tune the retention window to your data-governance policy. Test with GOVERNANCE before considering COMPLIANCE.