MP-7(1): Prohibit Use Without Owner

MP-7(1) is a deceptively small enhancement with big operational consequences: if your environment allows removable or portable storage, you need a clean, provable rule that no device gets used without an owner. “Owner” here is not a vague concept. Auditors and assessors expect a named person or accountable role who can be contacted, who accepts responsibility for the device’s custody and authorized use, and who can trigger response actions if the device is lost, stolen, or misused.

This requirement shows up in federal system assessments and contractor environments that handle federal data, where portable media risk intersects with data loss, malware introduction, and chain-of-custody gaps. Teams often stumble because they treat “ownership” as an HR concept rather than an access control gate. The practical outcome you want is simple: if a user plugs in an unregistered USB drive, the endpoint blocks it and logs the event; if the device is approved, the ownership record ties it to a responsible party and an allowed use case.

Use this page as a requirement-level runbook: who it applies to, how to implement, what evidence to keep, and what auditors commonly challenge.

Regulatory text

Excerpt: “NIST SP 800-53 control MP-7.1.” ¹

Operator interpretation (what you must do):
You must implement a control that prohibits the use of portable storage media when it does not have an assigned owner. “Prohibit” implies an enforced restriction (technical or procedural with effective gating), and “without owner” implies you maintain a recorded owner-of-record that can be validated during an assessment. ¹

What this means in practice:

• Every portable storage device that can connect to in-scope endpoints needs a documented owner.
• Your endpoints (or the systems controlling them) must deny or quarantine devices that lack ownership status.
• Exceptions must be explicit, time-bound, and approved by an accountable authority.

Plain-English interpretation of the requirement

The mp-7(1): prohibit use without owner requirement is a “no orphan media” rule. If you cannot answer “who is responsible for this device,” the device cannot be used on your systems.

Treat “owner” as a control attribute tied to the device’s identity (serial number, hardware ID, or other stable identifier), not a sticky label. Ownership should survive user turnover and be recoverable from a system of record. If a device is found in the environment and no ownership record exists, it is unauthorized by default.

Who it applies to (entity and operational context)

Entity types (common applicability):

• Federal information systems implementing NIST SP 800-53 controls. ²
• Contractor systems handling federal data (for example, in environments aligned to federal security requirements in contracts). ²

Operational scope (where it matters):

• Endpoints (workstations, laptops) that can accept USB mass storage.
• Admin workstations used for privileged access.
• Kiosks and shared devices.
• Build rooms, labs, and OT-adjacent environments where portable media is used for updates.
• Third-party operational contexts where suppliers or field services connect removable media to your assets.

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

Step 1: Define “portable storage media” and “owner” for your environment

Write a short standard that answers:

• Which media types are covered (USB drives, external SSD/HDD, SD cards, encrypted USB, portable optical media).
• Whether phones in “file transfer” mode count.
• What qualifies as an “owner” (named employee, service account with responsible manager, or role-based owner with an escalation path).

Operational tip: require an owner-of-record even for “shared team drives.” In that case, assign a primary accountable custodian (team lead or system owner) plus permitted user group.

Step 2: Establish the system of record for ownership

Pick one authoritative place to store device ownership and status:

• CMDB / asset inventory
• Endpoint management inventory
• A dedicated removable media register

Minimum fields to capture:

• Device identifier (serial number or hardware ID)
• Owner name and role
• Business justification / permitted use
• Data classification permitted
• Approval metadata (approver, date)
• Status (approved, blocked, lost/stolen, retired)
• Retention/disposition record when decommissioned

If you use Daydream as your control operating system, create a “requirement control card” for MP-7(1) with a single owner, trigger events (new device request, employee offboarding, incident), and exception rules so operations stays consistent across teams. ¹

Step 3: Implement enforcement: “no record, no mount”

Policy is not enough. Put a gate in the workflow:

• Endpoint device control: block USB mass storage by default; allow only whitelisted device IDs that have an owner record.
• MDM/endpoint management: enforce removable storage restrictions on managed devices.
• DLP/EDR telemetry: alert and optionally isolate on unauthorized media insertion attempts.

Design decision matrix:

Environment	Recommended enforcement	Evidence produced
Standard corporate endpoints	Block by default + allowlist approved devices	Device control policy + logs of blocked devices
Engineering / build labs	Allow only signed/encrypted media with owner record	Policy exceptions + lab SOP + logs
Admin workstations	Strict deny + no exceptions without security approval	Configuration baseline + exception approvals
Third-party field service	Provide company-owned media assigned to accountable internal owner	Issuance logs + return logs

Step 4: Create a controlled request-and-approval workflow

A fast, auditable workflow prevents “shadow USB” behavior:

1. Requester submits: purpose, data classification, device type, duration of need.
2. Approver validates business need and assigns owner-of-record.
3. Security/IT registers device ID and applies enforcement allowlist entry.
4. Device is labeled physically (optional) and issued with handling instructions.
5. Owner acknowledges responsibilities (loss reporting, no personal use, return on offboarding).

Keep the workflow lightweight. Your biggest risk is bypass behavior when approvals take too long.

Step 5: Define and manage exceptions (tightly)

Exceptions will happen (legacy equipment, incident response, emergency patching). Make them survivable in audits:

• Require written approval by a defined authority (system owner + security).
• Specify scope: which systems, which device, purpose, start/end condition.
• Require compensating controls: encryption, escort, logging, post-use scan.
• Track exceptions to closure.

Step 6: Run recurring control health checks

You need to show the control operates over time:

• Review logs for blocked unowned devices.
• Reconcile inventory: devices in inventory must have owners; owners must be active.
• Validate offboarding: owner departure triggers reassign or disable.
• Sample test: attempt to mount an unregistered device on a test endpoint and confirm it is blocked.

A practical way to keep this clean is to define a minimum evidence bundle per operating cycle (inputs, approvals, outputs, retention location) and schedule a control health check ticket that cannot be closed without attachments. ¹

Required evidence and artifacts to retain

Store evidence in a central, access-controlled repository aligned to your audit approach.

Minimum evidence set (high-confidence):

• Removable media / portable storage standard (definition of owner, scope, exceptions).
• Inventory/export showing each approved device, unique ID, and assigned owner.
• Screenshots or configuration exports of endpoint device control/MDM policy enforcing block-by-default.
• Change records showing approvals for new devices and updates to allowlists.
• Exception register entries with approvals and closure proof.
• Logs demonstrating enforcement (blocked events, allowed device mounts, alerts).
• Control health check results and remediation tracking to validated closure. ¹

Common exam/audit questions and hangups

Assessors tend to probe these areas:

1. “Show me the list of portable media allowed in the environment and who owns each.”
   Hangup: inventory exists but lacks unique identifiers or owners.

2. “How do you technically prevent unowned media from being used?”
   Hangup: policy says “don’t,” but endpoints allow it.

3. “What happens when an owner leaves the company?”
   Hangup: orphaned devices remain whitelisted.

4. “Do third parties ever connect portable media to your systems?”
   Hangup: no documented rules for supplier field work.

5. “How do you handle emergency or break-glass scenarios?”
   Hangup: ad hoc approvals with no record, later impossible to evidence.

Frequent implementation mistakes and how to avoid them

• Mistake: treating “owner” as “the person holding it today.”
  Fix: set owner-of-record and require reassignment through a workflow.

• Mistake: allowing “temporary” exceptions with no expiry condition.
  Fix: tie exceptions to a closure trigger (project end, ticket closed) and review open exceptions regularly.

• Mistake: allowlisting by vendor/model instead of device ID.
  Fix: allowlist by unique identifier so “approved USB” can’t be swapped for another.

• Mistake: ignoring non-USB portable storage paths.
  Fix: include SD card readers, external drives, and “phone-as-storage” modes based on your endpoints.

• Mistake: evidence scattered across email threads.
  Fix: require attachments in a single ticketing system or GRC workspace; Daydream-style control cards help keep ownership, cadence, and evidence expectations consistent. ¹

Enforcement context and risk implications

No public enforcement sources were provided for this requirement in the supplied catalog, so this page focuses on assessment and operational risk.

Risk you are managing:

• Data exfiltration via removable media.
• Malware introduction from uncontrolled devices.
• Loss of accountability when devices are found, lost, or used across teams without ownership records.
• Assessment failure when you cannot prove the “prohibit” mechanism works or cannot demonstrate a complete owner register.

The risk signature assessors look for is simple: unowned devices can be used, and you cannot prove otherwise.

A practical 30/60/90-day execution plan

First 30 days: Establish the rule and the register

• Publish a one-page standard defining portable media scope, owner-of-record, and exception authority.
• Stand up the ownership register (CMDB fields or a dedicated register).
• Decide enforcement approach for managed endpoints (block by default is the cleanest baseline).
• Build the request/approval workflow and template language for owner acknowledgment.

Days 31–60: Turn on enforcement and start collecting evidence

• Deploy endpoint controls in audit mode first (if needed) to see impact, then switch to enforced blocking.
• Register and approve required business devices; remove informal allowlists.
• Create the exception register and require approvals through a consistent workflow.
• Run your first control health check and open remediation items with owners and due dates.

Days 61–90: Prove sustained operation

• Reconcile inventory to reality: spot-check endpoints, validate registered device IDs, confirm owners are active.
• Test offboarding: ensure owner departure triggers reassignment or disablement of allowlisted devices.
• Package your evidence bundle for assessment: policies, exports, screenshots, logs, and health check results.
• Add recurring health checks to your control calendar, tracked to closure.

Frequently Asked Questions

Does “owner” have to be a specific person, or can it be a team?

Use a specific accountable owner-of-record whenever possible. If you must use a team, assign a primary custodian (named role) and document the escalation path so accountability is clear during an assessment.

Can we meet MP-7(1) with policy only, without endpoint blocking?

Policy-only implementations are hard to defend because the requirement uses “prohibit.” Most teams satisfy assessor expectations by enforcing block-by-default controls and keeping logs that show unregistered devices are denied. ¹

What device identifier should we record to prove ownership?

Record a stable unique identifier that your endpoint control tool can match reliably (commonly a serial number or hardware ID). Avoid identifiers that change when the device is reformatted.

How should we handle third parties who need to transfer files via USB during field work?

Prefer company-owned media issued under your register with an internal owner-of-record. If a third party must bring media, require pre-approval, register the device ID, and apply compensating controls such as scanning and strict system scoping.

Are encrypted USB drives required to satisfy MP-7(1)?

Encryption can be a strong compensating control, but MP-7(1) is about ownership and prohibition of unowned use. You can require encryption as a policy standard, but you still need an owner register and enforcement gate.

What evidence is most convincing to an auditor?

A device ownership export with assigned owners, endpoint policy configuration showing block-by-default with allowlisting, and logs of blocked unregistered devices. Pair this with exception approvals and a documented health check cadence. ¹

Footnotes

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

2. NIST SP 800-53 Rev. 5