SC-5: Denial-of-service Protection

SC-5: Denial-of-service Protection requires you to protect systems and services from denial-of-service (DoS) events by defining which DoS types matter in your environment and implementing controls to reduce their impact on availability and mission delivery. To operationalize it fast, assign an owner, document DoS scenarios, deploy layered technical mitigations, and retain recurring evidence that the protections work. ¹

Key takeaways:

• SC-5 is an availability control: you must plan for DoS conditions and reduce their impact on critical services. ¹
• Auditors look for two things: defined DoS event types (your parameters) and proof the protections are implemented and monitored. ²
• Evidence beats intent: configs, diagrams, runbooks, monitoring alerts, and incident records are what close SC-5. ¹

SC-5: denial-of-service protection requirement is one of those controls that gets “mostly implemented” technically, then fails in assessment because it is not defined, scoped, and evidenced. In practice, teams often have pieces (a WAF, rate limiting, a cloud DDoS service), but cannot show: (1) which denial-of-service event types they designed for, (2) where protections sit in the request path, and (3) how they know the protections work during real traffic spikes and attacks.

For a Compliance Officer, CCO, or GRC lead, the fastest way to operationalize SC-5 is to treat it as a control system with named ownership, defined DoS scenarios, and repeatable evidence collection. Your job is to make availability protection auditable across people, process, and technology. That means a short written standard, a mapped architecture, a runbook that operations actually follows, and monitoring/response records that show the organization can detect, absorb, and recover from DoS conditions. ¹

Regulatory text

SC-5 (excerpt): “{{ insert: param, sc-05_odp.02 }} the effects of the following types of denial-of-service events: {{ insert: param, sc-05_odp.01 }} ; and” ²

Operator interpretation (what you must do):

1. Define the parameter(s): Identify the “types of denial-of-service events” that are relevant to your system (for example, volumetric network floods, application-layer request floods, resource exhaustion, or upstream dependency failure modes). The control text is parameterized, so your environment must fill this in explicitly. ²
2. Implement protections to “protect against or limit the effects”: Put technical and operational measures in place so those DoS events do not take down critical services, or you can degrade gracefully and recover quickly. ¹

Plain-English interpretation of SC-5

SC-5 expects you to prevent or reduce outages caused by abusive traffic, misbehaving clients, or exhaustion of finite resources (bandwidth, CPU, memory, threads, database connections, queues). A passing implementation looks like: you have identified likely DoS modes, put controls at the right layers (edge, app, data stores, third-party dependencies), and can prove through monitoring and operational records that protections are active and maintained. ¹

Who it applies to (entity and operational context)

SC-5 applies to:

• Federal information systems and
• Contractor systems handling federal data, including cloud-hosted workloads, SaaS platforms, and hybrid environments where availability is part of mission, safety, or contractual performance. ²

Operationally, this control is most critical for:

• Internet-facing services (APIs, web apps, customer portals)
• Shared services (identity, DNS, email gateways, VPN/remote access)
• High-dependency platforms (payment flows, data ingestion pipelines, message queues)
• Systems with strict uptime commitments or mission impact if degraded

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

1) Assign control ownership and define scope

• Name a control owner (often Security Engineering, Network/Infrastructure, or SRE) and a GRC owner responsible for evidence quality.
• Define in-scope services: list the production applications, public endpoints, and critical internal services that must remain available.
• Document “DoS event types” for your environment (the SC-5 parameter). Keep it short and specific; assessments fail when this is vague. ²

Practical tip: write the DoS event types as “attack or condition → impacted resource → impacted service.”

2) Build a DoS threat-to-control mapping

Create a one-page matrix that links:

• DoS event type (volumetric, L7 flood, credential-stuffing-as-DoS, resource exhaustion, dependency outage)
• Entry point (CDN/WAF, API gateway, load balancer, VPN, DNS, email)
• Primary mitigations (what stops it)
• Detection signals (what alerts)
• Owner and runbook link

This becomes your SC-5 “map” and makes evidence collection deterministic. ¹

3) Implement layered technical protections (minimum viable set)

You do not need every possible control, but you need defensible coverage across layers.

Edge and network layer

• DDoS protection service (cloud provider or specialist)
• Network ACLs / security groups, geo/IP allow/deny where justified
• Upstream bandwidth and routing protections where applicable

Application layer

• WAF rules for common floods and abusive patterns
• Rate limiting and throttling at API gateway and application endpoints
• Request size limits, timeouts, connection limits
• Bot management/captcha where user experience allows

Resource protection (most common real DoS root cause)

• Autoscaling policies aligned to safe resource ceilings
• Circuit breakers and bulkheads between services
• Database connection pooling limits and query timeouts
• Queue backpressure and dead-letter handling to prevent cascading failure

Dependency resilience

• Multi-AZ / multi-region patterns where required by mission impact
• Health checks and failover behaviors
• Vendor/third party dependency monitoring (CDN, DNS, identity provider)

Tie each measure back to a DoS type you documented. SC-5 is easier to defend when every control has a stated purpose. ¹

4) Define operations: monitoring, runbooks, and on-call actions

Auditors will ask “How do you know it’s working?”

Minimum operational requirements:

• Dashboards for traffic rates, error rates, latency, saturation (CPU/memory), and dependency health
• Alerting tuned to DoS indicators (sudden traffic spikes, elevated 429/503s, connection pool exhaustion, WAF blocks)
• Runbook(s) that include triage steps, escalation, and how to enable stricter controls (tighten rate limits, switch WAF mode, block ASNs, add rules)
• Post-incident review template that captures root cause and control improvements

Your SC-5 story must show prevention plus response. ¹

5) Establish recurring evidence collection (make it automatic)

Create an “SC-5 evidence playlist” that is produced on a schedule and on-demand for audits:

• Monthly exports of WAF/DDoS summaries
• Change records for WAF/rate-limit policy updates
• Screenshots or PDFs of dashboards and alert definitions
• Tickets showing response actions during a spike/attack
• Architecture diagram showing where protections sit in the traffic flow

Daydream (as a GRC workflow) fits naturally here: map SC-5 to a control owner, an implementation procedure, and recurring evidence artifacts so you are not rebuilding proof every audit cycle. ²

Required evidence and artifacts to retain

Keep evidence tied to three questions: what you designed for, what you implemented, and what you monitor.

Design / scope

• SC-5 parameter statement: “DoS event types considered”
• System/service inventory with criticality tags
• DoS threat-to-control matrix
• Current architecture/network diagram (CDN/WAF/API gateway/LB/app tiers/data stores)

Implementation

• WAF policy exports, DDoS service configuration, rate-limit configs
• Load balancer and API gateway settings (timeouts, max connections, request limits)
• Autoscaling and resource quota configurations
• Secure change management records for DoS-related rule changes

Operations

• Monitoring dashboards and alert rules
• On-call runbooks and escalation paths
• Incident tickets and post-incident reviews involving traffic spikes or availability events
• Service level objectives (if used internally) and availability reports

Common exam/audit questions and hangups

Auditors and assessors tend to focus on these:

1. “What DoS event types are in scope for SC-5?” If you cannot answer in a sentence, you will scramble. ²
2. “Show me where protections are enforced.” They will want a diagram plus configs for edge/app controls.
3. “How do you detect and respond?” Expect requests for alert definitions and incident records.
4. “Is this consistent across environments?” They may sample multiple apps, not just your flagship service.
5. “How do third parties affect your DoS posture?” If CDN, DNS, or identity is external, show monitoring and failover planning.

Frequent implementation mistakes and how to avoid them

Mistake	Why it fails SC-5	Fix
“We have DDoS protection” with no defined event types	SC-5 is parameterized; you must state what you protect against. 2	Write a scoped list of DoS types tied to your architecture and risks.
Controls exist, but only for web traffic	APIs, VPN, DNS, and auth often become the DoS choke point	Expand scope to all critical entry points; document compensating controls.
Rate limiting breaks legitimate customers	Overly aggressive throttles cause self-inflicted DoS	Use tiered limits, allowlists for trusted integrations, and adaptive rules.
No evidence retention	You cannot prove control operation after the fact	Automate monthly evidence pulls and store them in your GRC repository.
Runbooks are theoretical	Response is inconsistent under pressure	Run tabletop tests; update runbooks from real incidents.

Enforcement context and risk implications

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

From a risk standpoint, SC-5 gaps show up as:

• Availability outages with customer impact and contract penalties
• Inability to meet federal system availability expectations
• Cascading failures where small spikes knock out shared dependencies

Assessors treat repeated availability incidents without control improvements as an indicator the control is not operating effectively. ¹

A practical 30/60/90-day execution plan

First 30 days (stabilize and define)

• Assign SC-5 control owner and GRC evidence owner.
• Define in-scope services and the DoS event types (SC-5 parameters). ²
• Create the DoS threat-to-control matrix.
• Gather baseline evidence: current WAF/DDoS configs, rate limits, dashboards, and one end-to-end architecture diagram.

By 60 days (implement gaps and standardize)

• Close top gaps from the matrix: missing rate limits, missing request bounds, missing dependency protections.
• Publish DoS runbooks and escalation paths; align on-call coverage.
• Standardize templates: WAF rule change tickets, incident postmortems, and monthly evidence exports.

By 90 days (prove operations and audit readiness)

• Run at least one DoS-focused game day or tabletop using your runbook outputs as evidence.
• Confirm evidence is collected on schedule and is reviewable without heroics.
• Prepare an “SC-5 assessment packet” in Daydream (or your GRC system): scope, parameters, control narrative, artifacts, and last review date. ¹

Frequently Asked Questions

What qualifies as a “denial-of-service event type” for SC-5?

It’s the set of DoS conditions you explicitly design for, based on your architecture and dependencies, such as volumetric floods, application-layer request floods, or resource exhaustion. The key is that you document your list and map protections to it. ²

We’re on a major cloud provider. Is turning on their DDoS service enough?

Often it covers volumetric attacks, but SC-5 usually also requires application-layer controls like rate limiting, timeouts, and resource protection. You still need to document your DoS types and show monitoring and response. ¹

How do we evidence SC-5 without running a live DDoS test?

Use configuration exports, monitoring/alert definitions, traffic dashboards, and incident records from real spikes or blocked attacks. Pair that with a tabletop exercise that shows the runbook works in practice. ¹

Does SC-5 apply to internal-only systems?

Yes, if loss of availability affects mission, safety, or contractual commitments, internal services can be in scope. Internal DoS often comes from misconfigurations, runaway jobs, or dependency failures, so document those event types too. ¹

How should we handle third-party dependencies (CDN, DNS, identity provider) under SC-5?

Treat them as part of your DoS event types and document mitigations like provider monitoring, fallback options, and operational response steps. Keep evidence that you monitor the dependency and have a response plan. ¹

What’s the fastest way to make SC-5 audit-ready?

Produce a single SC-5 packet: parameterized DoS types, a threat-to-control matrix, diagrams, configs, and recurring evidence exports. Then map ownership and evidence schedules in Daydream so it stays current between assessments. ²

Footnotes

1. NIST SP 800-53 Rev. 5

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