Protect stored and transmitted account data

“Protect stored and transmitted account data” sounds straightforward until you try to prove it under assessment pressure. Most findings come from two gaps: (1) teams can’t confidently enumerate every place account data exists or travels, and (2) encryption or key management is inconsistently implemented across a mixed environment (cloud, SaaS, legacy apps, endpoints, third parties). PCI DSS 4.0 frames this as a baseline obligation: account data must be safeguarded in storage and transit ¹.

Operationalizing the protect stored and transmitted account data requirement means turning a security intent into a controlled system: scoped data discovery, explicit data handling rules, approved cryptography patterns, hardened key lifecycle practices, and continuous validation. It also means aligning engineering, infrastructure, and third-party management so the control is true end-to-end, not just “in the database.”

This page gives you requirement-level implementation guidance: who it applies to, what to do in sequence, what artifacts to retain, the audit questions you will get, common mistakes, and a practical 30/60/90-day plan you can assign to owners.

Regulatory text

Excerpt (PCI-03): “Safeguard account data in storage and transit.” ¹

Operator interpretation (what you must do):

• In storage: Wherever account data exists (databases, files, logs, backups, object storage, data warehouses, endpoints, removable media), apply controls that prevent unauthorized access. Encryption is the standard pattern, but the control also depends on who can access the data, how keys are protected, and whether the data should exist at all ¹.
• In transit: Wherever account data moves (service-to-service calls, user-to-app, app-to-database, batch exports, SFTP, APIs, message queues), protect it from interception or modification. Practically, this means approved secure protocols, strong TLS configurations, and controls preventing downgrade or plaintext fallbacks ¹.
• Evidence expectation: You must be able to show a consistent, designed approach across the cardholder data environment and connected systems in scope, not one-off encryption settings.

Plain-English requirement: what “account data” protection means in practice

Treat “account data” as high-impact data that triggers strict handling. Your goal is to prevent three outcomes:

1. Unauthorized read access (data theft).
2. Unauthorized modification (integrity loss).
3. Uncontrolled propagation (data sprawl into logs, analytics, tickets, chat, vendor systems).

A workable interpretation for operators:

“We know where account data is, we keep the minimum necessary, and we enforce encryption and key controls everywhere it is stored or transmitted, including third parties.”

Who it applies to

Entities: Merchants and service providers that store, process, or transmit payment account data, or that can impact the security of that environment ¹.

Operational contexts where this becomes real work:

• Custom applications that handle payment flows (web, mobile, APIs).
• Cloud data planes (object storage, managed databases, Kubernetes secrets, snapshots).
• Observability tooling (logs, traces, error reporting, APM) that may capture request payloads.
• Backups and DR where encryption can be inconsistent.
• Third parties such as payment processors, call centers, support platforms, managed hosting, and incident response retainers that may receive account data.

What you actually need to do (step-by-step)

Use this sequence to operationalize fast and create assessment-ready outputs.

Step 1: Define scope and data elements (start with a data inventory)

Deliverable: A current “Account Data Inventory” that lists:

• Data elements considered account data in your environment.
• Systems that store it.
• Services and network paths that transmit it.
• Third parties that receive it.

How to execute:

• Map your payment flows using architecture diagrams plus system logs.
• Search for data patterns in data stores and logs (start with the highest-risk locations: logging pipelines, object storage, backups).
• Confirm where data crosses trust boundaries (VPC-to-internet, app-to-SaaS, batch exports to third parties).

Step 2: Minimize and control storage (reduce what you protect)

Deliverable: A “Data Minimization Standard” and an engineering backlog for removal.

• Remove account data from places it doesn’t belong (logs, analytics, test environments).
• Set retention rules and deletion workflows.
• Tokenize or truncate where business needs allow.

Practical control test: Can an engineer explain why each storage location is necessary, and show retention/deletion is enforced?

Step 3: Encrypt stored account data (at-rest patterns you can defend)

Deliverable: An “Encryption at Rest Design” for each storage class:

• Databases (managed or self-hosted)
• File systems and object storage
• Backups, snapshots, and replicas
• Endpoints or removable media (if applicable)

Implementation expectations to drive:

• Encryption enabled and enforced by policy (where platforms support it).
• Access controls prevent direct reads of raw encrypted blobs by broad roles.
• Separation of duties between data access and key administration, where feasible.

Step 4: Encrypt transmitted account data (in-transit standards)

Deliverable: A “Secure Transport Standard” specifying:

• Approved protocols (for example, TLS-based protocols for HTTP and service communications).
• Rules for certificate management and rotation ownership.
• Prohibited patterns (plaintext internal traffic by assumption, weak or deprecated protocols, or fallbacks).

Execution checks:

• Confirm service-to-service encryption, not just edge TLS.
• Confirm exports (batch files, integrations) use secure channels and are authenticated.

Step 5: Implement key management as a control, not a feature

Deliverable: A “Cryptographic Key Management Procedure” that covers:

• Key generation, storage, access, rotation, revocation, and destruction.
• Role-based access to keys with approvals.
• Logging/monitoring of key access and admin actions.
• Backup and recovery for keys (so encryption doesn’t break recoverability).

Key management failures are common because teams treat platform defaults as sufficient but cannot show lifecycle controls and access governance during assessment.

Step 6: Extend controls to third parties (contracts + verification)

Deliverable: A third-party “Account Data Handling Addendum”:

• Prohibit storage unless explicitly approved.
• Require encryption in transit and at rest (or equivalent contractual commitments).
• Require incident notification paths tied to account data exposure.

Also retain evidence that the third party’s handling matches your flow diagrams. If they receive account data, you need proof the transfer method is protected and the receiving system is controlled.

Step 7: Validate continuously (don’t wait for the assessor)

Deliverable: A repeatable “Account Data Protection Test Plan”:

• Test that data is not present in prohibited stores (log sampling, storage scans).
• Test encryption configuration drift (policy checks, configuration monitoring).
• Test transport security (scan endpoints; confirm internal service mesh or mTLS patterns if used).

If you use Daydream in your GRC workflow, treat this requirement as a single control family with mapped artifacts: inventory, diagrams, standards, key procedures, and validation results. That packaging reduces scramble time during assessments and renewals.

Required evidence and artifacts to retain

Keep these in a single evidence folder per environment (prod, staging if in scope) and per payment flow:

Artifact	What “good” looks like
Account Data Inventory	Systems, stores, flows, owners, and third parties listed and dated
Data flow diagrams	Clear trust boundaries and transmission paths called out
Data minimization/retention standard	Storage allowed/prohibited, retention rules, deletion process
Encryption at rest configs	Screenshots/exports/policy-as-code showing encryption enabled and enforced
Secure transport standard	Protocol requirements, certificate ownership, exceptions process
Key management procedure	Lifecycle steps, roles, access approval, logging expectations
Access control evidence	IAM role listings, least privilege reviews for stores and keys
Validation/testing results	Scan outputs, sampling logs, exception remediation tickets
Exceptions register	Each exception has risk acceptance, owner, expiry, compensating controls

Common exam/audit questions and hangups

Expect assessors and internal audit to probe these areas:

• “Show me everywhere account data is stored today. How do you know that list is complete?”
• “Do logs, traces, or support tooling capture account data?”
• “Show encryption settings for primary databases, replicas, snapshots, and backups.”
• “Who can access encryption keys? How is that access approved and reviewed?”
• “Where does account data leave your environment? How is it protected in transit to third parties?”
• “How do you prevent engineers from creating new storage locations with encryption disabled?”

Common hangup: teams can demonstrate encryption in one layer (for example, database storage encryption) but cannot show the same discipline for derived copies (exports, caches, backups, observability).

Frequent implementation mistakes (and how to avoid them)

1. Inventory by spreadsheet only. Fix: tie inventory to data discovery outputs and architecture diagrams; review it on a schedule tied to releases.
2. Edge-only TLS. Fix: document and enforce encryption for internal hops that carry account data, including service-to-database and batch processors.
3. Backups and snapshots forgotten. Fix: add explicit backup encryption checks and recovery tests to the validation plan.
4. Keys managed by “whoever has cloud admin.” Fix: define key admin roles, approvals, logging, and periodic access reviews.
5. Overbroad exceptions. Fix: time-box exceptions, require compensating controls, and track remediation tickets with owners.

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement. Treat the risk as practical and immediate: unprotected account data (stored or transmitted) increases breach impact, increases incident response complexity, and creates assessment findings that can affect your ability to attest to PCI DSS compliance ¹.

Practical 30/60/90-day execution plan

Assign one owner per workstream (AppSec, Infra, Data, IAM, Third-Party Risk).

Days 0–30: Get to “known state”

• Build the Account Data Inventory and baseline data flow diagrams.
• Identify all storage locations and transmissions tied to payment flows.
• Create a list of “high-risk sprawl” targets: logs, object storage, backups, tickets, chat exports.
• Draft encryption-at-rest and secure-transport standards; publish internally with an exceptions process.

Days 31–60: Implement and harden

• Remediate the biggest gaps: plaintext transfers, unencrypted stores, uncontrolled exports.
• Implement key management procedures with role definitions and approvals.
• Update third-party contracts or addenda for any third party receiving account data.
• Stand up validation: configuration checks and sampling to confirm data is absent from prohibited locations.

Days 61–90: Prove operations and prepare for assessment

• Run the test plan and retain outputs as evidence.
• Perform an internal “mini-assessment” interview: inventory completeness, key access controls, backup coverage, third-party transfers.
• Close or time-box exceptions; document compensating controls and sign-offs.
• Package evidence in Daydream (or your GRC system) so each artifact is mapped to the protect stored and transmitted account data requirement and is easy to retrieve.

Frequently Asked Questions

Do we have to encrypt every database if account data is tokenized?

If tokenization truly removes account data from the database, document that conclusion and verify the token vault and any re-identification service still meet storage and transit protections ¹. Keep evidence of where the original account data can exist and how it is protected.

What’s the fastest way to find accidental storage of account data?

Start with log aggregation, APM/error tools, object storage, and backups because they collect copies outside primary databases. Pair pattern-based searches with a review of app logging configuration and support workflows that may paste sensitive data.

Are internal network transfers in scope for “transmitted” protection?

Yes if account data traverses those links; internal traffic is still transmitted traffic from a protection standpoint ¹. Document the paths and enforce secure transport for each hop that carries account data.

What key management evidence do assessors usually want?

They want to see who can administer keys, how access is approved, how key actions are logged, and how rotation/revocation works in practice. Keep role listings, access review records, key policy exports, and sample log events of key administration.

How do we handle third parties that receive account data via support cases or email?

Treat that as a data flow you must control. Prohibit sending account data through unapproved channels, provide approved secure transfer methods, and add contractual handling requirements for any third party that might receive it.

Can we rely on cloud-provider default encryption settings?

You can use platform encryption features, but you still need to prove configuration, enforcement, and key access governance. Retain policy exports, screenshots, and access control evidence that shows the defaults cannot be bypassed without detection or approval.

Related compliance topics

• 2025 SEC Marketing Rule Examination Focus Areas
• Access and identity controls
• Access Control (AC)
• Access control and identity discipline
• Access control management

Footnotes

1. PCI DSS v4.0, PCI DSS Document Library