SA-17(4): Informal Correspondence

SA-17(4) sits in the System and Services Acquisition (SA) family and is aimed at a familiar problem: key security and architecture decisions often live in “informal” channels (email threads, Slack/Teams chats, ad hoc meeting notes, ticket comments) instead of formal design docs. If that material is not captured and retrievable, you end up with gaps in traceability during assessments, incident reviews, or system changes.

This requirement is easiest to implement if you treat it like a documentation and evidence-control problem across your software development lifecycle (SDLC) and third-party delivery model. Your job as a Compliance Officer, CCO, or GRC lead is to make sure developer communications that materially affect the system can be produced on demand, are retained for an appropriate period, and are accessible to the right internal roles (security, audit, compliance) without turning into uncontrolled data sprawl.

The practical approach: define scope, set rules for where work discussions happen, require developers to use approved systems, and retain artifacts in a controlled repository. Then build an evidence routine that proves the process runs the same way every time.

What SA-17(4) requires (plain-English interpretation)

SA-17(4): Informal Correspondence requires you to require the developer of the system, system component, or system service to support your need to obtain and review informal correspondence related to the build or delivery of that system/service ¹.

In practice, “informal correspondence” means development communications that may not be part of the “official” documentation set but still contain decisions and rationale that matter for security and compliance. Examples you should plan for:

• Email threads approving a design change that affects authentication or logging
• Chat messages discussing a hotfix for a vulnerability
• Ticket comments documenting why a control was implemented a certain way
• Meeting notes summarizing an exception decision or risk acceptance discussion

Your operational goal is simple: if an assessor asks “Why is this built this way?” or “How was this security change decided?” you can produce the supporting correspondence in a controlled, repeatable way.

Regulatory text

Excerpt: “Require the developer of the system, system component, or system service to:” ²

Operator meaning (what you must do):

• You must impose a developer obligation (internal dev teams and external third parties) that ensures informal correspondence relevant to system development and delivery is captured, retained, and made available as part of your assurance and assessment needs.
• Because the excerpt is a “require the developer…” construction, implementation usually lives in contract language, SDLC procedures, and evidence retention controls that you can demonstrate to assessors ³.

Who it applies to (entity + operational context)

This requirement commonly applies in these contexts ²:

• Federal information systems developed internally or by integrators
• Contractor systems handling federal data, including SaaS providers and service operators supporting federal missions

Operationally, scope it to:

• Product/application development teams (including DevOps/SRE when they deploy changes)
• External third parties that design, code, configure, or materially change the system/service
• Security engineering and compliance teams who need to retrieve artifacts
• Procurement/vendor management teams who must make it contractually enforceable

If you rely on multiple third parties (systems integrator + component supplier + managed service provider), treat SA-17(4) as a supply chain evidence requirement: each party must preserve and provide correspondence for their portion of the system.

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

Step 1: Define “informal correspondence” for your environment

Create a short standard that answers:

• Which channels count (email, chat, ticketing, code review comments, meeting notes)
• What topics are “in scope” (security architecture decisions, vulnerability remediation, access control changes, encryption choices, logging/auditing changes, exceptions/risk acceptance)
• What is out of scope (purely social chatter; routine scheduling unless it includes decision context)

Deliverable: Informal Correspondence Standard (one to two pages) mapped to your SDLC.

Step 2: Set approved systems and “where work happens”

Decide where you want discussions to occur so you can retain them:

• A ticketing system for decisions and approvals
• A code repo + pull request reviews for implementation discussion
• A managed collaboration platform with retention (if you allow chat-based decisions)

Rule of thumb: if a decision affects a control, require it to be summarized in a system-of-record artifact (ticket, ADR, PR description) even if the initial discussion happened elsewhere.

Deliverable: SDLC procedure update stating “security-relevant decisions must be recorded in X.”

Step 3: Put the developer obligation in contracts/SOWs (third parties)

For third-party developers, add clauses that require:

• Use of approved communication channels for in-scope work
• Preservation/retention of in-scope correspondence
• Cooperation and timely production to you and your assessors
• Secure transfer method and ownership/usage rights for provided artifacts
• Flow-down requirement to subcontractors (if permitted)

Deliverable: Contract/SOW language and a vendor due diligence checklist item tied to SA-17(4).

Step 4: Implement retention and access controls

Work with IT/security to define:

• Retention approach (what is retained, where, and under whose admin control)
• Access model (who can search and export, with audit logs)
• Legal hold capability (if your organization uses it)
• Segregation of customer data and sensitive data in correspondence

Deliverable: Retention configuration evidence and access control list for the tooling involved.

Step 5: Build an evidence collection routine (make it assessable)

You need a repeatable way to show the control runs:

• For each release or major change, require an evidence packet that includes links/exports to relevant tickets, PRs, and decision records
• For vulnerabilities, ensure remediation discussions are captured in the vulnerability workflow (ticket comments, RCA notes)
• Store the packet in a controlled repository used for audits (GRC tool, secure file store with permissions)

If you use Daydream for third-party risk and control operations, map SA-17(4) to a named control owner, attach the procedure, and set recurring evidence tasks so collection does not depend on tribal knowledge.

Deliverable: Release/change evidence packet template and a recurring evidence task.

Required evidence and artifacts to retain

Keep evidence that shows both design and operating effectiveness:

Governance and procedures

• Informal Correspondence Standard (scope + channels + rules)
• SDLC procedure showing how decisions are recorded
• Record retention standard covering collaboration systems (or a specific addendum)

Contracts and third-party proof

• Contract/SOW clauses requiring retention and production
• Third-party onboarding checklist showing the requirement was communicated
• Subcontractor flow-down language (where applicable)

Operating evidence (what auditors ask for)

• Sample set of tickets/PRs showing security decisions documented
• Exports or links demonstrating chat/email summaries were captured into the system of record
• Access control evidence for repositories and collaboration tools (role lists, audit logs)
• Evidence packets tied to releases, major changes, or security patches

Common exam/audit questions and hangups

Expect questions like:

• “Show me how you ensure developer communications are retained and retrievable.”
• “Where do security-relevant decisions get documented, and who approves them?”
• “How do you handle informal correspondence when development is outsourced?”
• “Can you produce correspondence supporting a specific security change?”
• “How do you prevent informal channels from becoming the only record?”

Hangups that slow teams down:

• No clear definition of what counts as “informal correspondence”
• Decisions scattered across tools with inconsistent retention settings
• Third parties claiming correspondence is proprietary or “not deliverable”
• Lack of a standard export/search process for collaboration platforms

Frequent implementation mistakes (and how to avoid them)

1. Mistake: Treating SA-17(4) as “save all emails forever.”
   Fix: scope it to security-relevant development decisions and require summaries in a system of record.

2. Mistake: No contract language, only an internal policy.
   Fix: add SOW obligations for external developers and require cooperation for assessments.

3. Mistake: Allowing Slack/Teams to be the final decision record.
   Fix: require an ADR/ticket/PR note that captures the decision, rationale, and approver.

4. Mistake: Evidence exists but is not searchable or exportable for audits.
   Fix: test retrieval quarterly by running a “produce the packet” drill for a real change.

5. Mistake: Subcontractors are invisible.
   Fix: require flow-down terms and identify all parties touching code/configuration early.

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement, so you should frame risk in assessment and operational terms rather than penalties.

Where SA-17(4) bites in real life:

• Assessment failure mode: you cannot demonstrate traceability for security decisions because the rationale lives in private inboxes or unmanaged chats.
• Incident response failure mode: you cannot reconstruct why a risky configuration shipped or who approved an exception.
• Third-party dispute mode: a developer refuses to provide records, or you lack the rights to obtain them.

This is why assessors often treat correspondence retention as part of broader SDLC assurance and supply chain control maturity ³.

Practical 30/60/90-day execution plan

First 30 days (foundation)

• Assign a control owner (usually AppSec, GRC, or Engineering Enablement).
• Define “informal correspondence” scope and approved channels.
• Inventory dev communication tooling (email, chat, ticketing, repo, meeting notes).
• Draft standard contract language for third-party developers.
• Identify one pilot system/release to test evidence collection end-to-end.

Days 31–60 (implementation)

• Update SDLC procedures: “security-relevant decisions must be recorded in X.”
• Configure retention and access in the selected tools.
• Roll contract language into new SOWs and renewals; add to third-party onboarding.
• Build the evidence packet template and a retrieval playbook (“how to produce artifacts”).

Days 61–90 (operationalize + prove it runs)

• Run a retrieval drill: pick a recent change and produce the correspondence-backed evidence packet.
• Fix gaps (missing ticket links, undocumented approvals, retention misconfigurations).
• Add recurring evidence tasks in your GRC workflow; Daydream can track the control mapping, owner, procedure, and scheduled evidence so audits don’t become a scavenger hunt.
• Train engineering leads and vendor managers on what must be captured and where.

Frequently Asked Questions

Does SA-17(4) mean we must archive every developer email and chat message?

No. Treat it as an obligation to preserve and produce informal correspondence that is relevant to system development and security decisions. Reduce sprawl by requiring decision summaries in a ticket, ADR, or pull request.

How do we handle informal correspondence when development is outsourced to a third party?

Put explicit retention and production requirements into the SOW/contract, including flow-down to subcontractors. Also require the third party to use your approved collaboration and ticketing systems for in-scope work.

What counts as “informal correspondence” in a modern DevOps workflow?

Common examples include chat threads, ticket comments, code review discussions, and ad hoc meeting notes where decisions are made. If it affects a control or security posture, it belongs in your retrievable record.

Our developers use Slack/Teams heavily. Is that automatically noncompliant?

Not automatically. The risk is when Slack/Teams becomes the only record of a security-relevant decision. Require a short, durable summary in a system of record and keep retention settings aligned to your audit needs.

Who should own SA-17(4) internally: Security, Engineering, or Compliance?

Engineering usually owns the workflow and tooling, Security/AppSec owns the security decision points, and GRC owns evidence and audit response. Assign one accountable owner and document the handoffs.

What’s the fastest way to prove operating effectiveness to an assessor?

Produce a release/change evidence packet that includes links or exports to tickets, PRs, and documented approvals showing how a security-relevant decision was made and retained. Then show you can repeat that process on demand.

Footnotes

1. NIST SP 800-53 Rev. 5 OSCAL JSON; NIST SP 800-53 Rev. 5

2. NIST SP 800-53 Rev. 5 OSCAL JSON

3. NIST SP 800-53 Rev. 5