Safeguard 4.9: Configure Trusted DNS Servers on Enterprise Assets

Safeguard 4.9 requires you to configure enterprise assets to use only trusted DNS servers, then prove the setting stays enforced over time. Operationally, that means defining “approved resolvers,” pushing DNS configuration via centralized management, blocking direct-to-internet DNS where possible, and retaining evidence that endpoints and network segments consistently resolve through your approved DNS path.

Key takeaways:

• Define and publish an “approved DNS resolver” standard (internal, third party, or hybrid) and apply it to every managed asset class.
• Enforce DNS settings through device management plus network controls that prevent bypass (rogue resolvers, hardcoded DNS, DoH where unmanaged).
• Capture recurring evidence: configuration baselines, exception approvals, and continuous verification reports tied to asset inventory.

The target keyword, safeguard 4.9: configure trusted dns servers on enterprise assets requirement, sounds simple until you try to prove it in an audit. “Trusted DNS” is not a brand name or a single technology choice. It is an operational posture: every enterprise asset should send DNS queries only to resolvers you approve, operate, and monitor (or that a vetted third party provides), with controls that reduce bypass.

For a CCO, GRC lead, or Compliance Officer, the fast path is to treat this as a configuration-and-monitoring requirement with measurable scope: endpoints, servers, and enterprise-controlled network paths. Your audit story should be straightforward: (1) documented standard, (2) technical enforcement, (3) monitoring/alerting for drift and bypass, (4) exceptions with risk acceptance, and (5) recurring evidence collection.

CIS Controls are not laws, but they are widely used as defensible security expectations and are often mapped into customer security questionnaires, procurement requirements, and internal control frameworks. Your goal is to operationalize 4.9 in a way that stands up to technical scrutiny without slowing the business. ¹

Regulatory text

Excerpt (provided): “CIS Controls v8 safeguard 4.9 implementation expectation (Configure Trusted DNS Servers on Enterprise Assets).” ¹

Operator interpretation: You must ensure enterprise assets are configured to use DNS servers you trust (approved resolvers), rather than arbitrary resolvers chosen by users, software, or local network settings. “Configure” implies this is not a one-time memo. You need technical enforcement and ongoing verification across the asset population. ¹

Plain-English interpretation (what an assessor expects)

A reasonable assessor will look for:

• A defined list (or criteria) of approved DNS resolvers for each environment (corporate network, remote users, cloud workloads).
• Centralized control over DNS client configuration on endpoints and servers.
• Guardrails that limit bypass (for example, blocking outbound DNS to anything except approved resolvers).
• Monitoring that detects drift, hardcoded DNS, and unexpected resolver usage.
• Evidence that the control runs continuously, not only at audit time.

Who it applies to

Entity applicability

• Enterprises and technology organizations implementing CIS Controls v8 as a security baseline. ¹

Operational context (where this gets tricky)

Safeguard 4.9 typically applies to:

• Managed endpoints: laptops/desktops, VDI, corporate mobile devices (where MDM controls DNS).
• Servers: on-prem, IaaS VMs, and managed server fleets.
• Network segments you control: office networks, data centers, and “known” egress points.
• Cloud networks: VPC/VNet DNS behavior, forwarders, and egress filtering for workloads.

It is harder (but still addressable) for:

• BYOD devices not enrolled in MDM.
• Partner networks and third-party-managed environments.
• Applications that embed DNS behavior (some security tools, containers, service meshes).

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

Step 1: Define “trusted DNS” for your enterprise

Document a DNS standard that answers, plainly:

• What are the approved resolvers (IP(s)/FQDN(s)) by environment?
• Are resolvers internal (AD DNS/BIND/Infoblox), third party, or hybrid?
• Do you require DNS security features (logging, filtering categories, DNSSEC validation, threat intel response)?
• What is allowed for remote users (VPN resolver, secure gateway resolver, ZTNA resolver)?

Artifact to produce: “Enterprise DNS Resolver Standard” (1–2 pages) mapped to Safeguard 4.9. ¹

Step 2: Map scope to asset inventory

You cannot enforce DNS settings if you cannot name the population.

• Pull your current asset inventory for endpoints, servers, and network segments.
• Categorize by management plane: Intune/MDM, SCCM/ConfigMgr, Jamf, GPO, Linux config management, cloud policies.
• Identify “out-of-management” assets and decide: enroll, isolate, or document an exception.

What auditors hang on: “How do you know this applies to all enterprise assets?” Your answer must be inventory-based, not anecdotal.

Step 3: Implement endpoint DNS configuration enforcement

Choose the mechanism per platform:

• Windows: enforce DNS server settings via GPO, MDM configuration profiles, or endpoint management baselines.
• macOS: enforce via configuration profiles (MDM) and restrict user changes where feasible.
• Linux: enforce through configuration management and standard images; manage systemd-resolved or resolver configs consistently.

Define a configuration baseline: “DNS resolvers must equal approved set; search domains must match environment; no local/rogue resolver.”

Control objective: endpoints should not be able to persistently set alternate resolvers without detection.

Step 4: Implement server and cloud workload DNS control

Servers often drift because teams “just change /etc/resolv.conf” to fix a deploy.

• Bake resolver settings into gold images and IaC templates.
• For cloud, document how workloads resolve DNS (cloud-provided DNS, custom forwarders, centralized resolvers).
• Where you run internal resolvers, define forwarder behavior and egress rules.

Practical tip: treat Kubernetes and containerized environments as a separate DNS domain. Cluster DNS settings often diverge from VM baselines.

Step 5: Add network enforcement to prevent bypass

Endpoint configuration alone is not enough when:

• Users roam to untrusted networks.
• Malware changes DNS.
• Applications hardcode DNS resolvers.

Network guardrails typically include:

• Restrict outbound DNS (UDP/TCP 53) from client networks to only approved resolvers.
• Monitor for unexpected DNS traffic patterns and resolver destinations.
• Decide how you will handle DNS-over-HTTPS (DoH): allow only approved endpoints, route through managed secure web gateways, or block where policy allows.

Your written requirement should be simple: “Enterprise networks block DNS to unauthorized resolvers, with exceptions approved and logged.”

Step 6: Monitor, alert, and prove ongoing operation

Define what “good” looks like:

• Endpoint compliance reports from your device management platform: DNS settings match baseline.
• Network telemetry: outbound DNS destinations limited to approved resolver IPs.
• Resolver logs: visibility into query sources, volume anomalies, and blocked domains (if you use filtering).

Then set an operating rhythm:

• Review compliance and exceptions on a scheduled cadence.
• Investigate noncompliant assets and remediate or isolate.

This is where Daydream fits naturally: map Safeguard 4.9 to a documented control, schedule recurring evidence requests from IT/network owners, and store screenshots/exports/config baselines so audit preparation is not a scramble. ¹

Required evidence and artifacts to retain

Keep evidence that demonstrates design and operating effectiveness:

Control design artifacts

• Enterprise DNS Resolver Standard (approved resolvers, environments, ownership).
• Network egress policy statement for DNS (what is blocked/allowed, exception path).
• Architecture diagram: endpoint → resolver → forwarders → upstream.

Operating effectiveness artifacts (recurring)

• Device management exports showing DNS configuration compliance by asset group.
• GPO/MDM configuration profile details (settings pages or exported policies).
• Firewall/secure gateway rules restricting DNS to approved resolvers.
• Logs or summaries from resolvers or network monitoring showing DNS traffic patterns.
• Ticket evidence: remediation of drift, investigation notes, and closure.

Exceptions and risk acceptance

• Approved exception register entries (asset, business justification, compensating control, expiration).
• Evidence exceptions are reviewed and closed or renewed.

Common exam/audit questions and hangups

1. “What are your trusted DNS servers?” Provide the authoritative list and who owns it.
2. “How do you enforce this on laptops off-network?” Show MDM-enforced settings and remote DNS routing approach (VPN/secure gateway).
3. “How do you prevent a user or malware from switching DNS?” Show endpoint restrictions plus network egress blocking/detection.
4. “Do you monitor DNS bypass like DoH?” Answer with your policy decision and technical controls.
5. “How do you cover cloud workloads and containers?” Show IaC templates, cluster DNS settings, and cloud network controls.
6. “Show me evidence this ran throughout the period.” Provide recurring reports and dated exports, not a single snapshot.

Frequent implementation mistakes and how to avoid them

• Mistake: defining “trusted” as “ISP DNS” or “whatever the router gives.” Fix: explicitly name approved resolvers and disallow DHCP-provided resolver changes on managed assets.
• Mistake: relying only on endpoint settings. Fix: add network egress restrictions and monitoring so bypass becomes visible or blocked.
• Mistake: ignoring remote users. Fix: document the resolver path for remote endpoints and enforce via MDM plus your remote access stack.
• Mistake: not scoping cloud and containers. Fix: include cloud DNS behavior in the standard and collect evidence per environment.
• Mistake: exception sprawl. Fix: require expirations and compensating controls, and tie exceptions to an owner.

Risk implications (why this control exists)

Untrusted DNS increases exposure to:

• Traffic interception and redirection.
• Command-and-control and phishing resolution.
• Data exfiltration patterns that hide in DNS.
• Loss of investigation visibility when DNS happens outside your logging perimeter.

From a governance angle, DNS is a shared dependency. If it is unmanaged, multiple downstream controls become harder to validate: web filtering, threat detection, incident response, and access controls that depend on name resolution telemetry.

Practical 30/60/90-day execution plan

First 30 days (stabilize and define)

• Publish the Enterprise DNS Resolver Standard (approved resolvers by environment).
• Identify owners: endpoint engineering, network, cloud platform, security operations.
• Pull asset inventory and classify by enforcement mechanism.
• Implement DNS configuration baseline for one major endpoint platform (pilot group) and one server environment.

Days 31–60 (enforce and reduce bypass)

• Roll out DNS enforcement broadly across managed endpoints.
• Implement network egress controls to restrict DNS to approved resolvers for core networks.
• Stand up compliance reporting: endpoint configuration compliance and network DNS destination monitoring.
• Create the exception register workflow with required fields and expiration.

Days 61–90 (operationalize and audit-proof)

• Expand coverage to remaining platforms (macOS/Linux/VDI) and cloud workloads.
• Decide and document your DoH stance; implement the corresponding technical control.
• Start recurring evidence capture (exports, screenshots, logs) stored in your GRC system.
• Run a tabletop audit: sample assets, prove configuration, show monitoring, show exception governance.

Frequently Asked Questions

What counts as a “trusted DNS server” for Safeguard 4.9?

A trusted DNS server is one your organization explicitly approves and can govern through configuration, contracts, and monitoring. It can be internal or provided by a vetted third party, but it must be named in your standard and enforced on assets. ¹

Do we have to run our own DNS resolvers to meet 4.9?

No. The requirement is to configure enterprise assets to use trusted DNS servers, not necessarily self-hosted servers. If you use a third party resolver, document approval, security features you require, and how you enforce endpoints to use it. ¹

How do we handle laptops that are off-network or rarely on VPN?

Enforce DNS settings through MDM and route DNS through your managed resolver path when possible (for example via always-on VPN or secure gateway). Where you cannot enforce routing, document compensating controls and treat it as an exception with an expiration.

Does Safeguard 4.9 include blocking direct DNS to the internet?

The safeguard language is about configuration on enterprise assets, but assessors often expect you to address bypass risk. Blocking or detecting direct-to-internet DNS at egress is a common compensating control to prove the configuration remains effective.

What evidence is strongest for audits?

Dated configuration exports (GPO/MDM profiles), compliance reports showing assets match the DNS baseline, and network rules limiting outbound DNS to approved resolvers. Pair that with an exception register that shows governance over deviations.

How can Daydream help without turning this into a documentation exercise?

Use Daydream to map Safeguard 4.9 to a single control statement, assign control owners, and automate recurring evidence requests (endpoint compliance exports, firewall rule screenshots, exception reviews). The point is steady evidence capture, not one-off audit prep. ¹

Footnotes

1. CIS Controls v8; CIS Controls Navigator v8