AU-16(2): Sharing of Audit Information

AU-16(2) is an operational control with a simple premise: sometimes audit information needs to cross organizational boundaries, and you need a repeatable, governed way to make that happen without leaking sensitive data or losing chain-of-custody. In federal environments and contractor ecosystems, this usually shows up as audit log excerpts, event timelines, SIEM alerts, incident-relevant telemetry, or audit summaries shared with an external oversight body, a customer, a prime contractor, a SOC, or an incident response partner.

The control is easy to misunderstand because it does not say “share everything.” It says to provide cross-organizational audit information to defined recipients, based on defined conditions. The work is in defining those parameters, converting them into a request-and-release workflow, and proving it operates consistently.

This page gives requirement-level implementation guidance for a CCO, compliance owner, or GRC lead: who must care, what to build, how to run it day to day, and what evidence auditors typically expect for the au-16(2): sharing of audit information requirement.

Regulatory text

Requirement (AU-16(2)): “Provide cross-organizational audit information to {{ insert: param, au-16.02_odp.01 }} based on {{ insert: param, au-16.02_odp.02 }}.” ¹

What the operator must do

• Name the recipients (the “to whom” parameter): define the external organizations/roles you will share audit information with (for example, a customer security team, a government SOC, an incident response retainer, a prime contractor, or an assessor).
• Define the conditions (the “based on” parameter): specify the triggering circumstances and constraints for sharing (for example, active incident response, contractual reporting obligations, authorized investigations, or time-bound support cases), plus guardrails such as data minimization and approval requirements.
• Execute sharing in a controlled way: implement a process that can produce audit information, sanitize it appropriately, transmit it securely, and record what was shared, when, and under what authority.

Reference framework context: AU-16 is part of the NIST SP 800-53 Rev. 5 Audit and Accountability family ².

Plain-English interpretation (what AU-16(2) means in practice)

You need an explicit, repeatable mechanism to share audit information outside your org without improvising. That mechanism must answer:

1. Who can receive audit information?
2. Under what circumstances is sharing allowed or required?
3. How do you ensure the shared data is accurate, limited to what’s needed, protected in transit, and traceable afterward?

In practice, most control failures happen because teams share logs informally (email/Slack screenshots), can’t reconstruct what was sent, or share too much (credentials, tokens, internal hostnames, customer data) because there is no sanitization standard.

Who it applies to (entity and operational context)

AU-16(2) commonly applies when you operate:

• Federal information systems and programs aligned to NIST SP 800-53 Rev. 5 ².
• Contractor systems handling federal data, including cloud/SaaS providers and managed service providers that must support customer or government-led monitoring and incident response activities ².

Operational contexts that trigger AU-16(2) work:

• Joint incident response (your team + customer/government/prime).
• Cross-tenant investigations where the customer requests evidence.
• External SOC monitoring where alerts and log excerpts flow to another organization.
• Contractual audit support, including security assessments where selected audit data is provided.

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

1) Define the “audit information sharing profile”

Create a short control appendix or standard that records:

• Approved recipients: list organizations and the allowed receiving roles or mailboxes.
• Permitted audit info types: e.g., authentication logs, administrative actions, API access logs, SIEM alert metadata, time-synchronized event timelines.
• Explicit exclusions: secrets, full packet captures, unrelated tenant data, content payloads unless explicitly authorized.
• Retention/handling expectations: how recipients must store or protect the data (contract clause or documented expectation).

Output artifact: “Cross-Organizational Audit Information Sharing Standard” mapped to AU-16(2). ¹

2) Define the “conditions for sharing” as decision rules

Convert “based on conditions” into a decision table your team can run.

Example decision table (adapt to your environment):

Trigger	Requestor	Allowed data	Required approvals	Transmission method	Required logging
Active security incident impacting requestor	Customer security contact	Incident-relevant time window logs, SIEM alert IDs	Security + Legal (if needed)	Encrypted portal/SFTP	Ticket + export hash
Contractual reporting obligation	Contract manager	Summary report, selected evidence	GRC + Security	Secure portal	Distribution record
Joint investigation with prime contractor	Prime SOC	Relevant event timeline	Security	Encrypted channel	Ticket + chain-of-custody

Your goal: remove ambiguity so the on-call lead is not making policy decisions under pressure.

3) Build a controlled request-and-release workflow

Implement a standard flow in your ticketing system:

1. Intake: requestor identity, organization, scope, timeframe, system(s), purpose, and urgency.
2. Validate authorization: confirm requestor is an approved recipient and trigger condition is met.
3. Scope and minimize: select smallest dataset that meets the purpose; redact nonessential fields.
4. Export with integrity: generate export from SIEM/log platform; record query parameters; compute checksums/hashes if your process supports it.
5. Approval: documented sign-off by designated approvers (Security, GRC, Legal, Privacy as needed).
6. Secure transmission: use approved methods; avoid ad hoc email attachments.
7. Recordkeeping: store what was shared (or a reproducible pointer), when, to whom, by whom, under what ticket, and under what conditions.
8. Post-share review: confirm receipt; record any follow-up restrictions or corrections.

Daydream tip (earned, not forced): teams often lose time proving steps 2–7. Daydream works well as the control system of record to map AU-16(2) to an owner, a runbook, and a recurring evidence set so you can answer assessors consistently without rebuilding the story each time. ¹

4) Align tool configuration to the workflow

You do not need exotic tooling, but you need consistency:

• SIEM/log platform saved searches for common share packages (by timeframe, system, event class).
• A “sanitization checklist” for exports (fields to remove; tenant filters; token scrubbing).
• Approved secure transfer mechanism (customer portal, encrypted file exchange, or equivalent).
• Central evidence repository with access control and retention rules.

5) Train operators and test the process

Run tabletop scenarios focused on audit info sharing:

• “Customer requests logs within 2 hours.”
• “Government SOC asks for event timeline for a suspected compromise.”
• “Prime contractor requests correlated identity events.”

Your test outcome should be observable: a completed ticket, approvals recorded, a securely transmitted package, and a retained evidence bundle.

Required evidence and artifacts to retain

Auditors assess this control through documentation and operational traces. Keep:

• Policy/standard defining recipients and conditions for sharing (AU-16(2) parameters). ¹
• Role/ownership assignment (control owner, backup, approvers).
• Runbook / SOP for request-intake, authorization checks, minimization, approvals, and transmission.
• Completed sharing tickets showing:
  • requestor identity and organization
  • condition/trigger selected
  • scope/time window
  • approval evidence
  • transmission record
• Export/query evidence: saved query, query parameters, and export metadata.
• Sanitization/redaction checklist attached to the ticket when applicable.
• Access logs for the evidence repository and transfer mechanism (where available).

Common exam/audit questions and hangups

Expect questions like:

• “Who are your approved cross-organization recipients for audit information?” (They want a list, not anecdotes.)
• “What are the conditions that permit sharing?” (They want decision rules.)
• “Show me the last instance of audit info shared externally and walk me through approvals and transmission.”
• “How do you prevent oversharing or disclosure of sensitive information in audit logs?”
• “How do you prove integrity and traceability of what you shared?”

Hangups that slow teams down:

• Audit info exists in multiple systems (cloud logs, IAM, EDR, SIEM), and there’s no single “export recipe.”
• Approvals are informal (verbal) and not captured in an auditable system.
• The team can show they shared something, but cannot show exactly what and why it was permitted.

Frequent implementation mistakes (and how to avoid them)

1. Mistake: Undefined recipients.
   Fix: maintain an approved recipient register tied to contracts, MOUs, or incident response agreements.

2. Mistake: “Conditions” are implied, not written.
   Fix: implement the decision table and require every ticket to tag the trigger condition.

3. Mistake: Oversharing raw logs.
   Fix: field-level minimization and redaction checklist; default to summaries unless raw is required.

4. Mistake: No chain-of-custody.
   Fix: require ticket ID, approver, export metadata, and transmission record for every share.

5. Mistake: Ad hoc transport.
   Fix: pre-approve transfer methods; block email attachments for audit exports if possible.

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement, so this page does not cite specific actions or penalties.

Risk-wise, AU-16(2) failures tend to show up as:

• Assessment findings: inability to demonstrate controlled external sharing or evidence of operation. ¹
• Incident response friction: delayed support to customers or government partners because you can’t export and share quickly.
• Confidentiality exposure: audit logs can contain sensitive identifiers; uncontrolled sharing can create reportable incidents depending on the data involved.

Practical 30/60/90-day execution plan

First 30 days (establish governance and scope)

• Assign AU-16(2) control owner and approvers.
• Draft the sharing standard: recipients, permitted audit info types, exclusions, and conditions.
• Inventory log sources and identify which systems can produce shareable exports reliably.

By 60 days (stand up the operational workflow)

• Implement the ticket workflow with required fields and approval steps.
• Define the decision table and embed it into ticket templates.
• Configure secure transfer method(s) and document the approved options.
• Create export/sanitization checklists and saved SIEM searches.

By 90 days (prove operation and harden)

• Run at least one internal exercise to generate a complete evidence package.
• Review a sample of recent tickets for completeness and tighten the checklist.
• Put recurring evidence collection on a cadence in your GRC system (Daydream or equivalent) so you can produce artifacts fast during assessments. ¹

Frequently Asked Questions

What counts as “cross-organizational audit information” under AU-16(2)?

Treat it as any audit-relevant telemetry you provide outside your organization: log excerpts, event timelines, SIEM alert details, or audit summaries. The key is that it supports accountability or investigation and crosses a formal boundary. ¹

Do we have to share raw logs, or can we share summaries?

AU-16(2) does not require raw logs; it requires providing audit information to defined recipients based on defined conditions. Use the minimum detail needed for the purpose, and document your decision rules. ¹

Who should approve external sharing of audit information?

Define approvers based on risk: Security for technical correctness and minimization, GRC for control alignment, and Legal/Privacy when the dataset could include regulated or contractual data. Record approvals in the ticket so you can prove the decision path. ¹

How do we handle multi-tenant SaaS logs without exposing other customers?

Build tenant filtering into your saved queries and add a sanitization checklist that verifies tenant scope before transmission. Require a second review for exports taken from shared infrastructure sources. ¹

What evidence is most persuasive to an assessor for AU-16(2)?

A completed sharing ticket that includes the request, the condition/trigger, approval records, export/query details, and a transmission record. Pair that with a written standard listing recipients and conditions. ¹

We share audit info through an MSSP/SOC. Does that satisfy AU-16(2)?

It can, if you’ve defined the MSSP/SOC as an approved recipient and you can show the conditions and method of sharing plus logs or tickets proving it occurs in a controlled way. Contract terms help, but operational evidence usually carries the assessment. ¹

Footnotes

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

2. NIST SP 800-53 Rev. 5