DE.CM-01: Networks and network services are monitored to find potentially adverse events

To meet DE.CM-01, you must continuously monitor your networks and network services for signs of potentially adverse events, then route detections into triage and response with provable coverage and review. Operationalize it by defining monitoring scope, logging and telemetry standards, alert logic, ownership, and evidence that monitoring runs and is periodically assessed. ¹

Key takeaways:

• Define scope and coverage for networks and network services (on-prem, cloud, SaaS, remote access) and document what is monitored and why.
• Centralize telemetry + alerting (logs, flow, DNS, identity, endpoint, cloud) with triage workflows and measurable SLAs.
• Keep an evidence bundle each review cycle: coverage map, configurations, alerts/metrics, exceptions, and management review notes.

The de.cm-01: networks and network services are monitored to find potentially adverse events requirement is a detection control: it expects you to know what is happening on your networks in time to act. For a CCO, GRC lead, or compliance officer, the practical challenge is translating a short framework outcome into an auditable operating model: what data you collect, what services you monitor, who watches alerts, how you escalate, and how you prove the control actually runs.

DE.CM-01 is frequently “claimed” with a tool purchase (SIEM, NDR, MDR), but auditors and customers typically test for coverage gaps (blind spots), operational drift (agents disabled, logs not ingesting), and governance gaps (no defined thresholds, no ownership, no review). Your objective is repeatable monitoring that covers critical network pathways and services, produces actionable detections, and feeds incident response.

This page gives requirement-level guidance you can execute quickly: scope definition, control design, step-by-step implementation, evidence to retain, common audit questions, and a practical execution plan. The language aligns to NIST CSF 2.0 outcomes and focuses on what you can show in an exam or diligence review. ¹

Regulatory text

Requirement (DE.CM-01): “Networks and network services are monitored to find potentially adverse events.” ²

What the operator must do:
You must implement monitoring across your network and network-delivered services (for example, DNS, VPN/remote access, identity paths that control network access, ingress/egress points, and cloud network layers) to detect suspicious or harmful activity. Monitoring must be operational, not aspirational: it has defined scope, produces detections, routes them to triage, and is reviewed for effectiveness. ¹

Plain-English interpretation (what “good” looks like)

DE.CM-01 means:

• You can see meaningful network activity (connections, authentication patterns, name resolution, egress, service access).
• You can detect conditions that indicate potential compromise, misuse, or policy violations.
• You can act because alerts flow into a monitored queue with documented ownership and escalation.
• You can prove it with artifacts showing coverage, configurations, alert volume/handling, and periodic review. ¹

A practical definition to adopt internally:

“All critical network paths and externally exposed network services generate security telemetry, are covered by detection logic, and are subject to routine health checks and management review.” ¹

Who it applies to (entity and operational context)

This applies to any organization running a cybersecurity program, with heightened relevance for:

• Critical infrastructure operators with operational dependencies on network availability and integrity. ¹
• Service organizations that host or process customer data, provide SaaS, managed services, or connectivity-enabled products. ¹
• Enterprises with hybrid estates: on-prem + cloud networks, remote workforce access, and third-party connectivity. ¹

Operationally, DE.CM-01 touches multiple teams:

• Security operations (SOC), IT/network engineering, cloud engineering, identity team, and incident response.
• GRC for scope definition, control ownership, evidence, and periodic control performance review. ¹

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

1) Define monitoring scope (the “coverage map”)

Create a scoped inventory of networks and network services you rely on, then mark what is monitored and how. Minimum categories:

• Network perimeters and egress points (internet gateways, NAT, proxies)
• Remote access (VPN, ZTNA, bastions)
• Core services (DNS, DHCP, NTP if managed, directory services that gate access)
• Cloud networking (VPC/VNet flow logs, firewall logs, load balancers, WAF if present)
• Third-party connections (site-to-site VPNs, private links, vendor-managed network appliances) ¹

Deliverable: a one-page Network & Network Services Monitoring Coverage Matrix showing asset/service → telemetry source → collection method → alerting coverage → owner. This converts the outcome into something testable.

2) Set telemetry standards (what must be logged/observed)

Write a short standard (1–2 pages) that answers:

• What log sources are mandatory (firewall, DNS, VPN, cloud flow, identity signals tied to network access)?
• Where logs are sent (SIEM/log platform) and who owns ingestion health?
• Minimum fields and time sync expectations (so investigations are possible)
• Retention expectations based on your risk and commitments (state your standard; don’t guess a regulator’s number) ¹

3) Centralize collection and validate ingestion health

Implement or confirm:

• Central log collection for the scoped sources.
• Ingestion health monitoring (alerts when a critical log source stops sending).
• Access control over logging systems (to prevent tampering) ¹

Operator tip: auditors often accept imperfect detection maturity if you can prove coverage + uptime monitoring of telemetry pipelines.

4) Define “potentially adverse events” in detection terms

Translate “potentially adverse” into a short detection catalog, mapped to your environment. Examples:

• Unusual outbound connections or data egress patterns from sensitive segments
• Connections to known suspicious destinations (based on your threat intel source)
• DNS anomalies (spikes, algorithmic-looking queries, newly seen domains used by many hosts)
• VPN anomalies (impossible travel, repeated failures, logins from new geographies if you track that)
• East-west movement indicators (new RDP/SMB patterns, admin tooling in unexpected segments)
• Cloud network policy violations (new security group openings, unexpected public exposure) ¹

Deliverable: Network Monitoring Use-Case Register (use case, data sources, detection method, severity, owner, response playbook link).

5) Build alert routing, triage, and escalation

Document and implement:

• Where alerts land (SIEM queue, ticketing system, MDR portal).
• Triage steps (validate signal, scope impact, contain if needed).
• Escalation rules (who gets paged, when IR is invoked).
• Service-level expectations you set internally (time-to-triage, time-to-escalate). These can be targets; you don’t need external citations because they are your operating commitments. ¹

6) Run periodic control performance reviews (make it auditable)

On a defined cadence, conduct a control review that covers:

• Coverage changes (new networks/services added without monitoring)
• Telemetry gaps (sources down, noisy/disabled detections)
• Alert outcomes (volume, false positives, confirmed incidents)
• Exceptions and remediation plans with owners and due dates ¹

This aligns directly with the recommended best practices: define outcomes/owners/metrics, run reviews, retain an evidence bundle. ¹

7) Integrate third-party risk (where networks depend on third parties)

If a third party provides network services (MDR, ISP-managed firewall, SaaS network edge, managed DNS), your due diligence should confirm:

• What telemetry you receive (logs, alerts, reports)
• Escalation paths and notification timelines
• Your right to evidence (tickets, incident reports, summaries)
• Coverage boundaries (what they do not monitor) ¹

Practical note: this is where Daydream fits naturally. Use Daydream to standardize third-party monitoring attestations, require evidence (sample alerts, monthly summaries), and track exceptions with due dates so DE.CM-01 doesn’t fail at your supplier boundary.

Required evidence and artifacts to retain (audit-ready bundle)

Maintain a concise evidence package per review cycle:

1. Monitoring coverage matrix (networks/services, telemetry sources, owners)
2. Logging/telemetry standard (what must be collected, where, and ownership)
3. SIEM/log platform configuration evidence (screenshots/exports showing ingestion for key sources, health monitoring enabled)
4. Detection/use-case register with version history and last review date
5. Sample alerts and case records (sanitized) showing triage, escalation, and closure
6. Ingestion health reports (missed logs, collector status, alerting on pipeline failures)
7. Control performance review notes: metrics, decisions, exceptions, remediation tickets, and sign-off ¹

Keep evidence focused on “is it monitored” and “can you show you responded.”

Common exam/audit questions and hangups

Expect questions like:

• “Show me your inventory of networks and network services and which ones are monitored.”
• “How do you know logs are being collected continuously and not failing silently?”
• “Who is on point for triage after hours, and what triggers escalation?”
• “What did you change based on your last review (noise reduction, new use cases, coverage fixes)?”
• “How do you handle monitoring responsibilities split across cloud, on-prem, and a third party?” ¹

Hangups:

• Over-reliance on a diagram with no proof of telemetry ingestion.
• Monitoring only perimeter firewalls while missing DNS, VPN, cloud flow, and SaaS/network edges that carry real signal.

Frequent implementation mistakes (and how to avoid them)

1. Tool-first, scope-later
   Fix: publish the coverage matrix first. Then map tools to it.

2. No definition of “network services”
   Fix: explicitly list services (DNS, VPN, load balancers, cloud networking layers) and assign owners.

3. No pipeline health monitoring
   Fix: alert on missing logs from critical sources and track failures as incidents or problems.

4. Alert fatigue with no tuning loop
   Fix: add a tuning workflow tied to the periodic control performance review. Document what was tuned and why.

5. Third-party blind spots
   Fix: bake telemetry access and reporting into contracts/SOWs; track exceptions in your third-party risk process. ¹

Enforcement context and risk implications

No public enforcement cases were provided for this requirement in the source catalog, so you should treat DE.CM-01 as a framework expectation rather than a standalone enforcement trigger. The practical risk is still material: weak network monitoring increases time-to-detect and can undermine incident response, customer notifications, and cyber insurance or contractual security commitments. ¹

Practical execution plan (30/60/90-day)

You asked for speed and operationalization; use this plan as a default and tailor to your environment and resourcing.

First 30 days (establish scope, ownership, and minimum telemetry)

• Publish the coverage matrix for networks and network services with named owners.
• Identify top gaps (unmonitored remote access, missing DNS logs, no cloud flow logs).
• Confirm central collection exists and enable ingestion health checks for critical sources.
• Stand up a basic use-case register with an initial set of detections and owners. ¹

Days 31–60 (make detections actionable and auditable)

• Implement alert routing into ticketing with severity, triage steps, and escalation contacts.
• Write the short logging/telemetry standard and get sign-off from Security + IT/Network.
• Run a first control performance review: document gaps, open remediation tickets, and set due dates. ¹

Days 61–90 (expand coverage and prove repeatability)

• Expand monitoring to remaining scoped services and third-party network dependencies.
• Tune detections using alert outcomes; document changes in the use-case register.
• Produce the first “evidence bundle” suitable for customer diligence or internal audit.
• If you use Daydream, configure DE.CM-01 tracking: owners, evidence requests, exception workflow, and review cadence so the control stays operable. ¹

Frequently Asked Questions

Does DE.CM-01 require a SIEM?

NIST CSF 2.0 does not mandate specific tools; it requires the outcome that networks and network services are monitored for adverse events. A SIEM is a common way to centralize telemetry and prove monitoring, but other architectures can meet the requirement if they produce equivalent evidence. ¹

What counts as “network services” for audit purposes?

Treat “network services” as the services that enable, route, or control network communications, such as DNS, VPN/remote access, firewalls, cloud networking layers, and externally exposed ingress services. Document your list and justify it in the coverage matrix. ¹

How do we prove we are “monitoring” and not just collecting logs?

Show alerting/detection logic plus triage records: sample alerts, tickets, escalation notes, and periodic review outcomes. Auditors look for a closed loop from telemetry to response and governance review. ¹

We outsource monitoring to an MDR. Are we still responsible?

Yes. You can delegate operations, but you still own the requirement outcome and must retain evidence of coverage, alert handling, and review. Add contract language for reporting and evidence access, and track exceptions like any other third-party risk. ¹

How do we handle cloud and SaaS where we don’t control the network?

Monitor the network controls you do have (cloud flow logs, security group changes, load balancer/WAF logs where applicable) and monitor identity and access paths that influence network exposure. For SaaS, require security event reporting and audit artifacts from the provider when network telemetry is inaccessible. ¹

What’s the minimum evidence set a CCO can ask for each review cycle?

Ask for the coverage matrix, ingestion health status for critical sources, a short list of key detections, a sample of alert tickets with outcomes, and a documented review with exceptions and remediation actions. That bundle usually answers the first wave of audit diligence questions. ¹

Footnotes

1. NIST CSF 2.0

2. NIST CSWP 29; Source: NIST CSF 1.1 to 2.0 Core Transition Changes