SC-41 Port and I/O device access: requirements and evidence

What SC-41 port and I/O device access asks for in plain words

SC-41 asks an organization to physically or logically disable or remove the connection ports and input/output devices that a system does not need, such as USB ports, optical drives and similar points where data can enter or leave a system. The control has two parts that you choose yourself. First, you define which systems or components it covers. Second, you define which ports or I/O devices must be disabled or removed on those systems. Once you have made both decisions, the requirement is to make the restriction actually happen, either by removing the hardware, blocking it in firmware or BIOS, or disabling it through logical controls. SP 800-53B does not assign SC-41 to any security or privacy baseline, so it applies to your system only if you select it through tailoring or an overlay.

The risk behind the control is data leaving a system without passing through your monitored network paths. A USB storage device, a writable optical drive or an unmanaged peripheral can copy sensitive files, carry malware in, or bypass the controls you have placed on network egress. Whether SC-41 matters for a given system depends on how sensitive its data is and how easily a person with local access could move it. The control is written to make you think about that exposure explicitly, rather than assume that a locked office or a managed laptop covers it.

Because the three organization-defined parameters are yours to set, SC-41 is mostly a scoping exercise. Your first task is to list the systems in scope and the specific ports and devices on each, and to record the reason each one is needed or not needed. A kiosk, a server room console and a developer workstation may each need a different answer. An assessor will expect to see that decision documented in system design documentation and configuration settings, and that the configured state matches it. Confirm with your assessor which systems they will sample and which configuration evidence they will request before you finalize the parameter values.

Which systems and devices SC-41 reaches once it is selected

SC-41 is not in any SP 800-53B baseline, so its reach depends entirely on what the organization selects and how it defines the ports and devices in scope. The cards below cover the decisions that change the workload: system classes, defined port types, shared and privileged ports, the link to AC-20 and MP-7, and the FedRAMP Rev5 position.

Endpoints and user workstations

Laptops and desktops are where USB storage, optical drives and card readers are most often used, so they are usually the largest part of SC-41 scope. Decide whether the control covers every endpoint class or only those that handle sensitive data. Check whether the configuration is enforced locally, through device management policy, or both, and record which ports are disabled and which are left open for documented business use.

Servers and data center hosts

Servers often have front-panel USB ports, serial consoles and optical drives that are rarely used after installation. Scope them by function: hosts in production enclaves may need the strictest settings, while hosts with out-of-band management may need a documented exception. Confirm with the platform team which hosts accept physical media for maintenance and how that access is logged.

Kiosks and shared public terminals

Kiosks and shared terminals exist to accept input from the public, so the defined ports are often the main attack path. Ask whether the organization needs to disable everything except a specific payment or scanning device, and whether those devices are fixed in hardware. Verify that tamper evidence and port locking are part of the physical controls, not only the software settings.

OT-adjacent and engineering hosts

Engineering workstations and historian servers near operational technology may need removable media to move firmware or logs across a boundary. Treat these as a separate scope decision, because disabling a port that a control system relies on can disrupt operations. Document the approved transfer method, the person who authorizes each use, and the compensating controls for the period when a port is open.

Shared and privileged ports

Some ports serve more than one function, such as a USB hub that carries both keyboards and storage, or a console port used for administration. Define in writing which ports are shared, which function must remain available, and how the logical block applies without disabling the required device class. Assessors will ask how you prevent a privileged port from being used by an unprivileged user.

Interaction with AC-20 and MP-7

AC-20 governs use of external systems, and MP-7 governs media use, so a removable drive connected to a system is often covered by both. Map each defined port to the controls that apply, so that the SC-41 implementation does not duplicate or contradict an MP-7 restriction. Check that the same device and port definitions appear in the system security plan and the media policy.

FedRAMP Rev5 position

FedRAMP's Rev5 baselines do not require SC-41 at Class B, C or D. An organization in a FedRAMP boundary can still select it as a risk decision, but the requirement does not come from the baseline. Ask the authorizing official whether the control is expected in the package, and record the answer so that a later assessor does not treat its absence as a gap.

How an assessor tests SC-41 using SP 800-53A

This table maps the single SP 800-53A determination statement for SC-41 to the examine, interview and test methods an assessor uses. Read each row as one step of the assessment, with the evidence to prepare and the findings that most often appear.

Assessment element	What the assessor does	Evidence to have ready	Common finding
Determination statement	Confirms that the defined ports or I/O devices on defined systems are physically or logically disabled or removed, using the organization-defined parameters	Written parameter values listing which systems and which connection points are in scope	Parameters left undefined or defined too broadly to test
Examine: system components	Inspects the in-scope systems and components to see whether the defined ports and drives are present, disabled or removed	Asset inventory with port and drive state per system, photographs or hardware records where physical removal is used	Ports that exist on a device class not covered by the inventory
Examine: design documentation	Reads the system design to confirm that unneeded connection points were removed or disabled as part of the intended design	Design documents naming the connection points retained and the reasons for each	Design silent on I/O devices, so the decision is undocumented
Examine: configuration settings and documentation	Reviews the configuration baseline, BIOS or firmware settings, OS device control policies and the related change records	Hardening baseline entries for USB storage, optical drives and firmware boot options, with approval records	Setting exists in a standard but was never applied to the production image
Examine: system architecture	Checks whether the architecture limits removable media and peripheral connections for each security zone	Architecture diagrams showing which zones permit removable media and why	Architecture diagrams that do not reflect the current deployment
Interview: administrators	Asks how ports are disabled, how exceptions are approved, how reimaged or replaced devices are handled, and who checks the state	Named owners, runbook for the control, and the exception approval process	Administrators describe a process that differs from the written procedure
Test: sample device	Selects sample devices and checks that the port or drive is actually unusable, for example by attempting to mount a device	Test results with date, device identifier, tester and observed behavior	Port is disabled in policy but still functional at the hardware or firmware level
Common finding: exceptions	Looks for devices or users with working ports that are absent from the approved exception list	Exception register with business justification, compensating controls and review dates	Undocumented exceptions discovered during sampling
Common finding: settings revert	Compares current device state with the baseline after reimaging or patching to see whether the disabling setting persisted	Repeatable build records and periodic configuration scan output	Disabled ports re-enabled after a reimage or a driver update

How to implement SC-41 in a fixed-scope engagement

This sequence turns SC-41 from a tailoring decision into a documented, tested set of port and I/O device restrictions that an assessor can trace from requirement to configuration to evidence. The organization owns the decisions and the control, while the implementation partner prepares the configurations and evidence.

Confirm the selection and tailoring decision
The organization's control owner confirms whether SC-41 is in scope for the system, since SP 800-53B does not place it in any baseline and it applies only when selected through tailoring or an overlay. The output is a written tailoring entry in the system security and privacy plan that records the selection, the rationale and the owner. Before work starts, the scope document should state that the organization owns the control and that the partner prepares systems and evidence only.
Define systems and port classes
The control owner fills in the three organization-defined parameters for SC-41 in the Release 5.2.0 catalog, naming the systems or components in scope and the connection points or I/O device classes to be disabled or removed, such as USB ports, optical drives or serial interfaces. The partner inventories the hardware and images in scope so the list matches what is actually installed. The output is a signed parameter sheet that maps each device class to the systems it applies to, and that sheet is the reference for every later step.
Choose the enforcement mechanism per class
For each device class, the team selects how the restriction will be enforced: firmware or BIOS settings, operating system device control, a port blocking tool, or physical removal or sealing where the hardware allows it. The choice depends on the platform, whether administrators need the port for legitimate maintenance, and whether the restriction must survive reimaging. The output is a decision record per device class that names the mechanism, the reason it was chosen, and the systems where a weaker mechanism is accepted.
Set configuration baselines
The partner writes the configuration baseline for each chosen mechanism, such as firmware settings, operating system policies or device control rules, and applies it to the golden images or build scripts used for the in-scope systems. The control owner reviews and approves the baseline under change control. The output is versioned configuration content stored with the system documentation, so that a rebuilt system receives the same restriction without manual work.
Verify on sample hardware
The team tests the baseline on a representative sample of each hardware model and operating system in scope, confirming that the blocked ports do not accept the restricted device classes and that permitted functions still work. Results are recorded as test cases with expected and actual outcomes, and failures are fixed and retested. Fleet-wide checks can then follow with a tool such as osquery or Fleet policies, and the team should confirm that the chosen tool reports the state it needs for the platforms in scope. The output is a signed test report that an assessor can examine.
Monitor configuration drift across the fleet
After rollout, the operations team checks that the restriction remains in place on every in-scope system, using configuration assessment or osquery-based queries that report device or setting state. Deviations open tickets under the organization's change and incident processes. The output is recurring evidence, such as scan results or policy pass and fail reports, retained according to the organization's record schedule.
Document exceptions with approvals
Where a business need requires a restricted port to stay open, the control owner records an exception that names the system, the device class, the business justification, the compensating measures such as monitoring or supervised use, and the approver. The exception carries a review date set by the organization. The output is an exception register that links each exception to the plan of action and milestones or risk acceptance record, so an assessor can see every deviation from the parameter sheet.
Hand over the evidence package
The partner assembles the evidence package: the parameter sheet, decision records, configuration content, test reports, monitoring output and exception register, mapped to the SC-41 determination statement and its examine objects. An independent assessor reviews the package and issues any findings or report, since the partner does not issue assessment results. The output is a handover pack and a short walkthrough with the control owner, and the organization decides what to submit to the assessor.

Choosing between disabling, removing and logically blocking ports

SC-41 asks for connection points that a system does not need to be taken out of use, and it allows that to happen either physically (removing or disabling the port in hardware, such as filling USB ports, removing optical drives or disconnecting cabling) or logically (blocking the device class in firmware, the operating system or an endpoint management policy so the port still exists but accepts no device). The choice is yours to make and document, and the organization owns it. Physical measures are hard to reverse without someone touching the device, which suits fixed servers, kiosks and shared workstations in controlled rooms. Logical measures can be applied across thousands of endpoints from one console, can be scoped to device classes, and can be changed without a site visit, but they depend on the operating system, the agent and the policy staying in place. A logical block that a local administrator can switch off is weaker evidence than a port that is physically sealed.

For endpoints, most organizations combine both: logical blocking of mass storage and removable media classes for the general population, with physical controls reserved for high-value or shared machines. Servers usually need the opposite emphasis, because the console or management ports are a legitimate access path that must stay open under SC-2 and AC-6 governance, so the reviewer should confirm which ports are actually defined as in scope before anyone disables anything. Shared workstations raise a separate question, since a logical policy tied to a user account may not apply when a different person logs on. Ask who can change each setting, where the configuration is recorded, and whether the policy applies to the device or to the user.

Legitimate exceptions, such as approved encrypted media for a specific team, should be recorded as named, time-limited decisions with an owner, a business reason, the device identifiers covered and the compensating controls, such as encryption enforced by policy and logging of each connection. Review them on a fixed schedule and remove any exception that no longer has a reason. Your assessor will look for the decision record, the approval and the review history, and will test whether the exception is applied only to the devices named. Confirm with your own security and procurement teams how exceptions are approved and retained, because the answer depends on your environment and governing policies.

Evidence that passes an SC-41 assessment

An assessor testing SC-41 looks for proof that the defined ports and device classes are actually disabled or removed, and that the organization can explain every exception. The cards below cover the artifacts that carry that proof and the routines that keep them accurate between assessments.

Defined parameter list

SC-41 has three organization-defined parameters, so the first artifact is a document that names the systems or components in scope, the connection ports or I/O device types to disable or remove, and the method for each (physical removal, logical disablement or both). Assessors compare the system inventory against this list. A parameter list that says "all USB ports" without naming the systems it covers leaves the assessor guessing what was tested. Confirm that the values match the tailored baseline your authorizing official approved.

System design and architecture documents

Design documents show where ports and I/O devices exist in the architecture and which components are expected to expose them. Examine objects for SC-41 include system design documentation and system architecture, so these pages are read directly. Keep a current diagram that marks hardened endpoints, kiosks, servers and thin clients, and note which ones carry a documented business need for a port. Stale diagrams that omit a recently deployed workstation model are a common reason assessors open findings.

Configuration baseline exports

Configuration exports are the strongest technical evidence for SC-41. Export the effective settings that disable USB mass storage, optical drive access or unused serial and parallel interfaces from the managed fleet, and keep the export tied to a baseline version and a date. Osquery can capture device and kernel module state across hosts, and Wazuh can check configuration against custom policies. Confirm that the exported settings reflect the enforced state, not only the policy intent.

Sampled device test records

Assessors test SC-41 by sampling devices, so keep dated records showing that each sampled device blocks the defined ports or device classes. Record the device identifier, the test method, the observed result and the tester. Fleet policies that ask whether a device has a port disabled, and show which devices pass or fail, produce this record continuously. Retain failed checks along with their remediation, since a clean sample with no history of corrections can look staged.

Exception register with approvals

Some systems need a port for a documented function, such as a scanner, a licensed hardware token or a lab instrument. Each of these belongs in an exception register that names the device, the port or device class, the business justification, the compensating measures, the approver and an expiry or review date. Assessors check whether exceptions are approved by the right authority and whether they are reviewed. An exception without an approver or review date will usually be recorded as a deficiency.

Change records and review cycle

Change records show that port configurations were managed after the initial build. Link each change to a ticket that describes the affected device class, the reason for enabling or disabling a port, the approver and the post-change check. Set a recurring review, at a frequency your own policy defines, that compares the current fleet state against the parameter list and the exception register. Ask whether removed ports are also reflected in the hardware procurement standard, since a new laptop model with a different port set can silently reopen the gap.

What meeting SC-41 costs in money and effort

Tooling is the most visible cost, but for SC-41 it is often the smallest part of the total. The control asks you to disable or remove unneeded connection points, and the tools that check that state can be open-source. Commercial endpoint management suites add licence fees, while self-hosted options shift the cost to hosting and the staff who run them.

Licence lines: Ask whether the quote includes any commercial endpoint management, device control or hardening licence, and whether those fees recur annually.
Open-source options: Wazuh, Fleet and osquery can check port and device state on monitored hosts without a licence fee. Their cost is infrastructure, storage and staff time.
Hosting: Self-hosted servers, databases and storage for the tooling are usually a recurring cost in your own cloud or data center.
Hardware changes: Locking USB ports or replacing drives with fixed media is a one-time purchase, but may need replacement cost later.

Before accepting any quote, confirm which tools are included, which are your responsibility to license, and what the monthly or annual run cost is for each.

Open-source tools that produce SC-41 evidence

This table compares four self-hosted open-source tools that can show whether USB ports, optical drives and other connection points are disabled or blocked across endpoints. Read each row for what the tool checks, the license named in its supplied facts, and the kind of SC-41 evidence it can help produce. None of these tools satisfies SC-41 alone; the organization must still define the ports in scope and the method used to disable them.

Tool	License	What it checks for SC-41	Evidence it supports
Wazuh Security Configuration Assessment	GPL-2.0-only	Scans monitored endpoints against YAML policies, mostly based on CIS benchmarks, that check files, registry keys and processes for configuration settings	Scan results showing whether device-restriction settings match the organization's defined baseline on each endpoint
Fleet policies	MIT	Asks yes or no osquery questions of each device, such as whether a defined connection port is disabled	Pass and fail counts per policy, showing which devices on each fleet are compliant and which need remediation
osquery	Apache-2.0 OR GPL-2.0-only	Queries hardware events and related system state as SQL tables, and osqueryd schedules these queries across a fleet	Scheduled query results and hardware event records that show device connection activity over time
Velociraptor hunts	AGPL-3.0-only	Collects defined artifacts from groups of endpoints, and schedules offline machines to report when they reconnect	Collected device state from machines that were offline during the first scan, plus a notebook per hunt for analysis

Who owns SC-41 and who can help

Your organization owns SC-41. Under the control, it is the organization that decides which connection points on which systems or components must be disabled or removed, and it sets the three organization-defined parameters that the Release 5.2.0 catalog leaves open. Because SC-41 is not in any SP 800-53B baseline, your team also decides whether the control is selected at all, through tailoring or an overlay, and records that decision in the system security plan. Your team is accountable for any exception and for the risk accepted when a port must stay open for a business reason.

Parameter decisions: Define which systems, which ports or device classes, and which removal method (physical or logical) apply.
Selection and tailoring: Record whether SC-41 is selected and why, in the system security plan.
Exception approval: Approve, time-bound and document any open port, such as a required keyboard or token reader.
Operational ownership: Keep configurations, owners and review dates current as hardware changes.
Assessment liaison: Provide the assessor with access to systems, documentation and people.

Before engaging anyone, confirm internally who signs off the parameters and exceptions, since no partner or auditor can make those decisions for you.

Where SC-41 implementations usually fall short

SC-41 is easy to state and hard to keep true. The gaps below appear when a port control is written as policy but never tied to defined parameters, managed devices and recorded exceptions. Each card names one gap and the step that closes it.

Undefined organization-defined parameters

SC-41 has 3 organization-defined parameters, and an assessor cannot test a requirement the organization never filled in. Teams often write "disable unneeded ports" without naming the systems in scope, the ports or device classes covered, or the mechanism used. Close it by completing each parameter in the system security plan and naming the component types it covers, so the examine step has a defined target.

Settings that drift after reimaging

A USB restriction applied to a golden image can disappear when a host is rebuilt, patched by a different team or restored from an older backup. The configuration then matches the policy on paper but not on the device. Close it by comparing live port settings against the approved baseline on a schedule, and treating any reimaged host as unverified until its checks pass.

Unmanaged devices outside the fleet

Port controls only apply to machines the monitoring tooling can see. Lab systems, kiosks, shared workstations and devices bought outside standard procurement often sit outside the fleet, so no query ever reports their state. Close it by maintaining a complete inventory of in-scope components and reconciling it against enrolled endpoints, so every unenrolled system is either brought under management or documented as excluded.

Unrecorded exceptions

Engineers often need a USB storage device for a vendor update or an optical drive for a legacy application. When these exceptions are granted verbally or in a ticket that is never linked to the system record, the assessor finds ports open with no approved reason. Close it by logging each exception with an owner, a reason, a compensating control and an expiry date, and reviewing the list before each assessment.

Policy intent without device state

A written procedure that says ports are disabled shows intent, but it does not show what the devices are doing. Assessors look for objective evidence from the systems themselves, such as configuration settings and test results. Close it by pairing each policy statement with a recurring machine-generated check that reports the actual state of each in-scope device, and keeping the output with the assessment record.

Checks that no one reviews

Compliance queries can run correctly for months while failing results go unread, which leaves the control in place only on paper. An organization that cannot show who reviewed failing devices and what was done about them gives an assessor little to accept. Close it by assigning a named owner to review failing results on a fixed cadence and recording the remediation or exception decision for each one.

Questions buyers ask about SC-41

Is SC-41 required by default under NIST SP 800-53?

No. SC-41 Port and I/O Device Access is not assigned to any security or privacy baseline in SP 800-53B, so it applies only when your organization selects it through tailoring or an overlay, or when a contract, agency or assessor requires it. Appendix C of SP 800-53 Rev. 5 lists it as implemented by the organization and the system. Before adding it, confirm with the authorizing official or contract owner whether the control is in scope for your system. FedRAMP's Rev5 baselines do not require SC-41 at Class B, C or D, according to the FedRAMP Rev5 control reference, so check the specific FedRAMP class your system targets.

What does SC-41 actually ask an organization to do?

SC-41 asks you to physically or logically disable or remove the connection ports and input/output devices you have defined as unnecessary on the systems you have defined. In practice that means deciding which ports matter (for example USB, optical drives, serial or other connection points), where each one applies, and how each one is turned off, whether by hardware removal, BIOS or firmware settings, operating system policy or device management rules. The control has three organization-defined parameters in Release 5.2.0 and no enhancements, so most of the work is in defining those parameters clearly and documenting them.

How long does SC-41 take to implement, and what drives the effort?

No public NIST source gives a duration for SC-41, so treat any timeline as something to scope with the people doing the work. The main drivers are the number of system types in scope, how many ports and device classes you must address on each, whether settings are already enforced centrally, and how many exceptions you need to document, such as hardware that must keep a port for a clinical, lab or industrial function. Environments with fleets managed by a central tool usually need less manual effort than environments where each host is configured by hand. Ask for the effort breakdown by system type and by port class in any written scope.

Can our in-house team implement SC-41 without an outside partner?

Often yes, if the team already manages endpoints and configuration centrally. The work splits into a policy and design step (defining the ports, systems and exceptions, and writing them into the system security plan), a configuration step (applying the disablement through firmware, operating system or device management settings), and an evidence step (showing an assessor that the settings are in place and stay in place). Teams without endpoint management, or without a process for documenting exceptions, usually find the evidence step takes the longest. Decide early who owns each step, because the organization owns the control even when an outside party helps.

What does our team need to provide for SC-41 work?

Plan to provide an inventory of the systems and components in the authorization boundary, the current configuration baseline for each device class, and a list of the ports and I/O devices in use across them. You will also need a named owner for the control, the approval record for any exception, and access to the systems so changes can be tested. NIST's SP 800-53A procedure for SC-41 expects an assessor to examine system design documentation, configuration settings and associated documentation, and system architecture, so those artifacts should exist and match what is deployed.

What does an assessor check for SC-41, and what evidence passes?

SP 800-53A Release 5.2.0 assesses SC-41 through one determination statement, using examine, interview and test methods. The examine objects are the systems or components, system design documentation, system configuration settings and associated documentation, and system architecture. An assessor will typically compare the documented list of disabled ports against the actual configuration settings on sampled systems and ask staff how the settings are enforced. Evidence that passes usually includes the approved parameter definitions, configuration exports showing the settings, and records of any approved exceptions. Confirm the specific evidence expectations with your independent assessor before you collect it.

What does an outside partner change about SC-41 assessment?

An implementation partner prepares the configuration, the documentation and the evidence, but it does not decide whether the control is satisfied. DeployOpen plans, implements, hardens and documents self-hosted open-source platforms inside your own infrastructure, and it can prepare systems and evidence for an assessment. Only the independent assessor or auditor issues findings, reports or certifications. The main change an outside partner brings is a fixed written scope, so the port list, systems covered and evidence deliverables are agreed before work starts. Ask any partner to show which parts of SC-41 they implement and which remain with your team.

Which open-source tools can produce evidence for SC-41?

Several open-source tools can show whether ports and devices are configured as documented, though none of them selects the control for you. Wazuh's Security Configuration Assessment scans monitored endpoints against YAML policies, mostly based on CIS benchmarks and extendable with custom checks, and recommends remediation. Fleet policies ask yes or no questions of devices as osquery queries, and its policies page shows which devices pass or fail each one. osquery exposes hardware events and other host data as SQL tables, and osqueryd can schedule queries across a fleet. Confirm that a chosen tool can check the exact port and device settings you define before relying on it as evidence.

How DeployOpen prepares SC-41 evidence

DeployOpen works on SC-41 as an implementation partner. We prepare the systems, configuration and evidence that show which connection points are disabled or removed on the defined systems, while your organization keeps ownership of the control and an independent assessor issues any conclusion about it.

How we scope

Agree in writing which systems and components fall under SC-41 and why they were selected
Record which USB, optical drive and other I/O interfaces are defined as unneeded for each system
Confirm whether SC-41 is selected through your tailoring or an overlay, since no SP 800-53B baseline includes it
Engagements are fixed-scope, with deliverables and timelines agreed before work starts

How we build

Configure ports and I/O devices to be disabled or removed on the defined systems, using settings your team approves
Document the chosen method, whether physical removal or logical disablement, for each system class
Deploy open-source checks such as osquery queries or Wazuh configuration assessment policies to confirm the settings persist
Run security testing to confirm that the disabled connection points cannot be re-enabled by ordinary users

How we hand over

Provide system design documentation and configuration settings that match the defined parameters
Deliver the query and scan results an assessor would examine for SC-41 on the in-scope components
Map the evidence to the related controls AC-20 and MP-7 so reviewers can follow the connections
Hand over runbooks so your staff can repeat the checks and explain them to an assessor

How we support

Offer ongoing support, upgrades and continuous testing as a retainer after handover
Re-run configuration checks when hardware, images or endpoint policies change
Review evidence again when your organization changes its tailoring decisions for SC-41
Coordinate with your independent assessor on questions about the evidence, without issuing any opinion ourselves