RA-5(4): Discoverable Information

The ra-5(4): discoverable information requirement sits in the Vulnerability Monitoring and Scanning control family, but it is really about managing what your system “tells the world” before an attacker even runs an exploit. Most security teams do some of this informally (hardening, banner reduction, DNS hygiene), yet struggle to show a tight chain from: (1) what is discoverable, to (2) what actions are required, to (3) proof those actions happen consistently.

RA-5(4) forces that discipline. You must determine what information about the system is discoverable, then take actions defined by your organization (the control includes an organization-defined parameter). ¹ For a Compliance Officer, CCO, or GRC lead, the fastest path is to turn this into a measurable operational routine: define categories of discoverable information, assign owners, set acceptance thresholds, and require evidence from engineering that exposure is reduced or explicitly risk-accepted.

This page gives requirement-level implementation guidance you can hand to infrastructure, security operations, and application teams and then audit against.

Regulatory text

“Determine information about the system that is discoverable and take {{ insert: param, ra-05.04_odp }}.” ¹

Operator meaning: you must (1) identify what information can be discovered about the system (typically without authentication or with low effort), and (2) take your predefined actions to address that exposure. The second half is intentionally customizable: you must specify what actions your program requires (for example, reduce banners, restrict unauthenticated endpoints, remove sensitive metadata, monitor exposure, or formally accept risk).

Plain-English interpretation (what the requirement is really asking)

RA-5(4) expects you to manage “pre-attack intelligence leakage.” That includes:

• Service and version disclosures (HTTP headers, SSH banners, SMTP banners, error pages).
• Network and DNS metadata (public DNS records, zone transfer risks, SPF/DMARC details, subdomain sprawl).
• Certificate transparency and TLS details (SANs that enumerate hostnames, weak ciphers, expired certs).
• Publicly reachable management planes (admin consoles, open ports that should not be internet-facing).
• Application metadata (stack traces, verbose errors, exposed API docs, unauthenticated status pages).
• Cloud and storage exposure signals (public buckets, open repos, exposed container registries).

You are not required to make the system “undiscoverable.” You are required to know what is discoverable and take your chosen actions consistently, with evidence.

Who it applies to

Entity scope

• Federal information systems.
• Contractor systems handling federal data. ¹

Operational scope (where it shows up in practice)

• Internet-facing applications, APIs, and SaaS admin portals.
• External DNS zones, CDN/WAF configurations, and TLS/certificate management.
• Cloud environments with public IPs, load balancers, gateways, and object storage.
• Internal environments where “discoverable” still matters (east-west scanning, partner networks, shared service networks).

If you have multiple systems, treat RA-5(4) as system-specific: each system should have its own discoverable information profile, actions, and exceptions.

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

1) Define “discoverable information” categories and required actions

Because RA-5(4) includes an organization-defined action parameter, write a short standard that answers two questions:

1. What counts as discoverable information for your system?
2. What actions are mandatory when it is found?

Practical required-action options you can standardize:

• Reduce: remove/obfuscate banners and headers that disclose product/version.
• Restrict: limit exposure (IP allowlists, auth gates, network segmentation).
• Harden: enforce secure configurations (TLS policy, disable debug modes).
• Monitor: alert on changes to external exposure (new ports, new DNS records).
• Accept: document a time-bound exception with risk sign-off.

Deliverable: a one-to-two page “RA-5(4) Discoverable Information Standard” with owners and review cadence.

2) Build the discoverable information inventory ¹

Create a repeatable inventory that is not just a spreadsheet of ports. Include:

• External footprint: domains/subdomains, public IP ranges, exposed services, certificate SANs.
• Technology disclosures: headers, banners, error messages, robots.txt, API specs visibility.
• Administrative access points: management endpoints, jump hosts, remote access gateways.
• Data exposure signals: unauthenticated file listings, public buckets, exposed logs/metrics endpoints.

Data sources you can use (pick what fits your environment):

• External scanning results (your vuln scanner, attack surface tooling).
• DNS and certificate transparency monitoring outputs.
• Cloud inventory (accounts/subscriptions/projects), asset inventories, CMDB.
• Manual validation for critical endpoints (what an unauthenticated user can see).

Deliverable: “Discoverable Information Register” tied to the system boundary.

3) Set thresholds and decision rules (what is acceptable vs. not)

Operators move faster with clear decision rules. Define:

• Always unacceptable: public management interfaces, default credentials, debug endpoints, directory listing, unauthenticated sensitive admin APIs.
• Conditionally acceptable: product family disclosure without version, generic server headers, public status pages with limited detail.
• Acceptable: necessary public DNS, required ports for service, public certificates with controlled SANs.

Deliverable: a decision matrix (see below) and an exception workflow.

4) Execute remediation through change control

Turn findings into work:

• Create tickets with the exact exposure, evidence, and required action.
• Assign to the correct owner (platform, app, network, cloud).
• Track through to closure with proof (before/after scan, config diffs, screenshots).

Deliverable: tickets and change records mapped to each finding.

5) Validate reduction and prevent regression

RA-5(4) is weak if it is one-time. Add:

• A recurring scan or monitoring job for external exposure drift.
• Alerting when new ports/services appear or DNS expands unexpectedly.
• Gate checks in CI/CD or infrastructure-as-code reviews (for example, policies preventing public admin endpoints).

Deliverable: recurring scan schedule, monitoring alerts, and control checks.

6) Formalize exceptions and risk acceptance

Some discoverable details are unavoidable. Require:

• Documented rationale, compensating controls, and expiration.
• Security and system owner approval.
• Re-validation when the system changes.

Deliverable: an RA-5(4) exception register.

Decision matrix (use this to drive consistent actions)

Discoverable item	Example	Default action	Evidence to retain
Version-revealing banner/header	“Server: nginx/1.x”	Reduce or suppress	Header capture before/after; config baseline
Public management plane	Admin console exposed	Restrict or remove	Firewall/WAF rule; network diagram update
Excessive DNS exposure	Unused subdomains	Remove; monitor	DNS change record; inventory update
Verbose errors	Stack traces	Harden app config	Screenshot/log sample before/after; release note
Public cert SAN sprawl	Many hostnames	Re-issue with constrained SANs	Cert issuance record; CT monitor output

Required evidence and artifacts to retain

Auditors will ask for proof you “determined” and “took action.” Keep:

• RA-5(4) standard: definitions, required actions, owners, exception rules. ¹
• Discoverable Information Register per system: dated snapshots and delta notes.
• Scan results (external and relevant internal views) showing discoverable info.
• Remediation tickets/change records: assignment, fix details, closure evidence.
• Configuration baselines: header policies, TLS policies, WAF rules, DNS standards.
• Exception approvals: documented risk acceptance with expiry and compensating controls.
• Recurring validation evidence: latest run outputs, alert rules, monitoring dashboards.

If you use Daydream to map RA-5(4) to a control owner, implementation procedure, and recurring evidence artifacts, treat the Daydream control record as your “single source of truth” and link each artifact to it for fast exam response.

Common exam/audit questions and hangups

Expect these:

• “Show how you determine what is discoverable for this system.” Bring your register plus the last scan outputs.
• “What actions do you take when you find discoverable information?” Point to the standard and a closed remediation example.
• “How do you know it stays fixed?” Show recurring scans/monitoring and at least one regression caught and remediated.
• “Where are exceptions approved?” Produce the exception register with expiration dates and sign-offs.
• “Is this aligned to your system boundary?” Tie findings to the system’s defined boundary and inventory.

Hangup: teams show a vulnerability scan report but cannot show a specific RA-5(4) workflow for banners, DNS sprawl, certificate SANs, or public admin endpoints. Your register and decision matrix solve this.

Frequent implementation mistakes and how to avoid them

1. Treating RA-5(4) as “just vuln scanning.” Fix: explicitly include non-CVE discoverables (DNS, headers, cert metadata, error verbosity).
2. No defined “actions.” Fix: write the required actions and thresholds; auditors will look for the organization-defined part. ¹
3. Point-in-time inventory. Fix: add recurring validation and drift monitoring.
4. Evidence scattered across tools. Fix: map artifacts to the control record (Daydream or your GRC) and standardize naming and retention.
5. Exceptions without expiry. Fix: require expirations and re-validation after major changes.

Enforcement context and risk implications

No public enforcement cases were provided in the supplied source catalog for this requirement, so you should treat RA-5(4) primarily as an assessment and breach-resilience control rather than an enforcement-driven mandate.

Risk-wise, discoverable information increases the chance of:

• Faster attacker recon and targeting of known-exploitable versions.
• Expanded attack surface through forgotten subdomains and exposed services.
• Credential and session targeting if admin portals are exposed.

For CCO/GRC: position this as reducing avoidable exposure and improving audit posture by demonstrating control operation with repeatable artifacts. ²

Practical 30/60/90-day execution plan

First 30 days (stand up the control)

• Assign a control owner and system-level SMEs (network, platform, app).
• Publish the RA-5(4) standard: categories + required actions + exception workflow. ¹
• Build the first Discoverable Information Register for the highest-risk system (internet-facing).
• Run an initial external discovery pass and open remediation tickets for high-risk exposures.

Days 31–60 (remediate and institutionalize)

• Close the highest-risk items (public management planes, verbose errors, major banner/version leaks).
• Implement baseline configurations: header sanitization, TLS policy, DNS hygiene checks, WAF rules.
• Create the evidence binder structure in your GRC (or Daydream): where each artifact lives and how it is linked.

Days 61–90 (make it durable)

• Add recurring scanning/monitoring for exposure drift; define who triages alerts.
• Test the audit story: pick one finding, show “discovered → ticketed → fixed → re-validated.”
• Expand the register to additional systems and third-party hosted components in your boundary.
• Run an exception review and remove expired or unjustified exceptions.

Frequently Asked Questions

What counts as “discoverable information” under ra-5(4): discoverable information requirement?

Treat it as anything an external party can learn about your system with low effort, especially without authentication: ports, services, banners/headers, DNS metadata, certificate SANs, and verbose application errors. Document your categories in an RA-5(4) standard. ¹

Do I need specialized attack surface management tooling to meet RA-5(4)?

No. You need a defensible method to determine discoverable information and evidence that you take defined actions. Many teams start with scanner outputs, DNS/cert monitoring, and cloud inventory exports, then mature into dedicated tooling as the footprint grows. ²

How do I handle business-necessary discoverability, like public APIs and public DNS?

Put them in the register as “intentionally discoverable,” then document compensating controls (auth, rate limits, WAF, monitoring) and set boundaries on what you will not expose (management planes, debug endpoints). Use time-bound exceptions when you cannot meet the standard immediately.

What evidence is strongest for auditors?

A dated discoverable information register, the standard that defines required actions, and at least one complete remediation trail with before/after proof and re-validation results. Keep exception approvals with expirations. ¹

How does RA-5(4) relate to third parties?

If a third party hosts or operates components inside your system boundary (cloud hosting, managed platforms, SaaS with dedicated instances), their configuration can create discoverable information. Flow your standards into contracts and onboarding, then validate through scans and attestations tied to your register.

What is the fastest way to make this “audit-ready” in a GRC tool?

Create a control record for RA-5(4) with a named owner, a written procedure, and a fixed set of recurring evidence artifacts (scan output, register snapshot, remediation sample, exception log). Daydream is a practical way to keep that mapping clean and to prompt evidence collection on schedule.

Footnotes

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

2. NIST SP 800-53 Rev. 5