SC-7(10): Prevent Exfiltration

SC-7(10): prevent exfiltration requirement means you must put technical controls at and around network boundaries to stop sensitive information from leaving your environment without authorization. Operationalize it by defining “exfiltration” for your data types, enforcing egress controls (filtering, proxy, DLP where justified), and keeping evidence that blocking, alerting, and response actions work in production ¹.

Key takeaways:

• Treat exfiltration prevention as an egress control program, not a single tool.
• Focus on high-risk paths first: internet egress, cloud storage sharing, email, and admin channels.
• Auditors look for two things: enforced technical controls and repeatable evidence of operation ².

The sc-7(10): prevent exfiltration requirement sits under NIST SP 800-53’s boundary protection family (SC-7) and pushes you past “we monitor” into “we actively stop.” You are expected to prevent unauthorized outbound transfer of information, which usually means controlling egress traffic, restricting protocols and destinations, and detecting and blocking suspicious data movement patterns ¹.

For most organizations, the operational challenge is scope and clarity. “Exfiltration” can mean a compromised endpoint uploading a database to a file-sharing site, an admin copying logs to personal storage, a third party support engineer pulling data through a remote tool, or a misconfigured cloud bucket that allows broad sharing. Your job as a CCO or GRC lead is to translate that into a control statement with owners, a procedure that engineers can run, and evidence artifacts you can produce on demand.

This page gives requirement-level guidance you can implement quickly: applicability, step-by-step execution, audit-ready evidence, common traps, and a practical 30/60/90 plan tied to how assessors test SC-7(10) in real environments ².

Regulatory text

Requirement (excerpt): “Prevent the exfiltration of information; and” ³.

Plain-English interpretation

You must stop unauthorized outbound movement of information. “Prevent” implies more than logging; it implies enforced controls that block or contain outbound flows that violate policy. In practice, that means:

• You identify which information types matter (for example, federal data, controlled unclassified information, sensitive customer data).
• You control the outbound paths where that data could leave (network egress, cloud sharing, email, remote access, removable media where applicable).
• You produce evidence that the controls are configured, active, and reviewed ².

Who it applies to

SC-7(10) commonly applies in these contexts ³:

• Federal information systems subject to NIST SP 800-53 control baselines.
• Contractor systems handling federal data, including hybrid environments where federal data is processed or stored in SaaS/IaaS.

Operationally, it applies wherever you have:

• A network boundary or logical boundary (internet gateways, cloud VPC/VNET egress, SaaS tenant controls).
• Users and workloads that can send data out (endpoints, servers, CI/CD runners, support tooling).
• Third parties with access paths (managed service providers, customer support platforms, incident response retainers).

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

1) Define “exfiltration” for your environment

Write a short, enforceable definition that engineers can implement:

• In-scope information types (tie to your data classification standard).
• Unauthorized destinations (personal email, personal cloud storage, unknown domains, non-approved regions).
• Unauthorized methods (unsanctioned file transfer tools, outbound SSH from servers, public sharing links) ².

Deliverable: a one-page “Exfiltration Prevention Standard” that maps data classes to allowed egress channels.

2) Map and prioritize egress paths (start with the choke points)

Create an egress inventory that is concrete enough to configure controls:

• Internet egress points (NAT gateways, secure web gateways, firewall clusters)
• Email gateways
• DNS resolvers and outbound DNS
• Cloud storage sharing controls (S3, Azure Storage, Google Cloud Storage, and SaaS storage)
• Remote access tooling (VPN, ZTNA, remote support)
• Administrative data export paths (SIEM export, ticketing attachments, log forwarding)

Prioritization rule that works in audits: start with paths that can move bulk data and paths with weak identity binding (shared accounts, legacy protocols).

3) Establish enforceable egress control objectives

Turn the definition into testable objectives. Examples:

• All outbound web traffic from corporate endpoints goes through a controlled proxy or secure web gateway, except documented break-glass cases.
• Outbound firewall rules default-deny for server subnets; allowlists exist for required destinations and ports.
• Cloud storage prohibits public access by default; public sharing requires exception approval and logging.
• Email outbound filters block or quarantine messages with sensitive data patterns for selected data classes.

Keep objectives tied to “prevent,” meaning a block, quarantine, or hard control where feasible ².

4) Implement technical controls (choose controls that create a hard stop)

You do not need every technology category, but you must cover the major outbound paths.

Network egress filtering

• Egress firewall rules with least privilege on ports and destinations.
• Separate policies for user subnets vs. server/workload subnets.
• Block known risky protocols outbound unless explicitly required (for example, outbound SMB from workstations).

Web and DNS controls

• Secure web gateway / proxy policies to block unsanctioned file sharing and risky categories.
• DNS filtering to block known malicious domains and newly registered domains if your risk posture supports it.

Cloud tenant and storage controls

• Prevent public access at the tenant level where possible.
• Restrict cross-tenant sharing and link-based sharing for sensitive data repositories.
• Require encryption and strong identity for any external sharing workflows.

DLP or content-aware blocking (targeted) Use DLP where the data type and volume justify it (email, web uploads, cloud drive sharing). Keep scope narrow at first: high-sensitivity labels, specific repositories, or regulated data fields. Broad “scan everything” deployments often stall due to false positives.

Endpoint controls (where egress controls are insufficient)

• Block unapproved exfil tools (unsanctioned sync clients).
• Control removable media if it is a credible path for your environment.

5) Add detection and response hooks that prove prevention works

Even strong egress controls need monitoring and a response play:

• Alert on policy blocks that indicate attempted exfiltration (bulk upload blocked, repeated destination blocks).
• Correlate with identity signals (privileged accounts, abnormal geolocation) where possible.
• Write a short “Suspected Exfiltration” playbook: triage steps, containment options, escalation, and evidence preservation ².

6) Operationalize exceptions without breaking the control

Assessors commonly find SC-7(10) gaps in exception handling. Implement:

• A documented exception process with business justification, owner, expiry, and compensating controls.
• A review cadence tied to change management.
• Technical tagging where possible (firewall rule objects or proxy policy groups labeled “exception”) so you can report on it.

7) Test prevention, then keep proving it

Prevention must be demonstrable:

• Run controlled tests (for example, attempt to upload a labeled test file to a blocked destination).
• Validate that blocks create tickets or alerts and that someone reviews them.
• Include control verification in routine change windows so new network routes or cloud services do not bypass controls.

Required evidence and artifacts to retain

Build an evidence set that matches how auditors ask questions.

Control documentation

• Exfiltration Prevention Standard (definition, scope, allowed channels)
• Network boundary and egress architecture diagram
• Egress control procedure (who changes rules, how approvals work)
• Exception register (requests, approvals, expirations)

Technical configuration evidence

• Firewall/proxy/DNS policy exports or screenshots showing egress allowlists/blocks
• Cloud tenant settings exports (public access blocks, sharing restrictions)
• DLP policies (scope, rules, enforcement actions)

Operational evidence

• Change tickets for policy updates and exception approvals
• Alert samples and incident/ticket evidence showing investigation of blocked attempts
• Test records (test plan, date, results, remediation actions)

Practical tip: package evidence by “egress path” so you can answer, “How do you prevent exfiltration via web/email/cloud sharing?” with a consistent binder.

Common exam/audit questions and hangups

Expect questions like:

• “Show me where you prevent outbound data transfer, not just detect it.” ²
• “What are your authorized egress points? Prove traffic can’t bypass them.”
• “How do you handle cloud sharing links and public access?”
• “How are exceptions governed, time-bounded, and reviewed?”
• “Demonstrate a test or recent event where an exfil attempt was blocked and triaged.”

Common hangup: teams show a SIEM dashboard and call it “prevention.” Assessors usually treat that as detection, not prevention, unless it triggers an enforcement action.

Frequent implementation mistakes and how to avoid them

1. Relying on endpoint DLP alone

• Fix: start with network and cloud choke points. Endpoint DLP can be additive, not foundational.

2. Allow-any outbound from servers “because apps need internet”

• Fix: require app owners to document destinations; implement allowlists by environment and owner.

3. Cloud storage “public access block” enabled, but sharing links still wide open

• Fix: treat “public” and “external sharing” as separate settings and test both paths.

4. No exception expiry

• Fix: require expirations and a review workflow. Make exceptions visible in reports.

5. No proof

• Fix: schedule recurring control verification and save outputs in an audit-ready folder structure. Daydream can help by mapping SC-7(10) to a named control owner, an implementation procedure, and a recurring evidence checklist so you do not rebuild the audit package each cycle ³.

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement, so you should treat SC-7(10) as an assessment and contractual risk driver rather than tying it to specific penalties here ³. The practical risk is straightforward: exfiltration is a common end-state of compromise, and assessors will flag weak egress control as a material control gap because it increases the blast radius of credential theft, malware, and insider misuse.

Practical 30/60/90-day execution plan

First 30 days (stabilize scope and choke points)

• Name a control owner and backups; document RACI across network, cloud, endpoint, and SecOps.
• Publish the Exfiltration Prevention Standard (draft is fine) tied to data classification.
• Inventory egress points and identify any unmanaged outbound routes.
• Implement or tighten basic egress rules at primary gateways; start allowlisting for server subnets.
• Stand up an exception register with expiry and approvals.

Days 31–60 (enforce and instrument)

• Roll proxy/SWG enforcement for user traffic where feasible; document bypass cases.
• Lock down cloud storage public access and external sharing defaults; verify with tests.
• Deploy targeted DLP controls for one or two high-value channels (email and web uploads are common starting points).
• Create alert routing and a “Suspected Exfiltration” playbook; run a tabletop on one realistic scenario.

Days 61–90 (prove operation and harden)

• Run prevention tests against each critical egress path; capture results and remediation.
• Audit exceptions and remove stale rules.
• Add continuous monitoring metrics you can show an auditor (policy block trends, top destinations blocked, time-to-triage).
• Package an assessor-ready evidence set mapped to SC-7(10) and store it with change tickets and test artifacts.

Frequently Asked Questions

Does SC-7(10) require a DLP tool?

NIST’s excerpt requires prevention of exfiltration, not a specific product category ³. You can meet the intent with strong egress filtering and cloud sharing restrictions, then add DLP where content-aware blocking is needed.

What counts as “prevention” versus “detection” for auditors?

Prevention means the control can block, quarantine, or otherwise stop the outbound transfer under defined conditions ². Detection-only controls generate alerts after data leaves, which typically will not satisfy “prevent” by themselves.

How do I scope exfiltration prevention in a SaaS-heavy environment?

Treat SaaS tenants as boundaries: restrict external sharing, control exports, and enforce identity-based access and logging ². Document which SaaS platforms can store sensitive data and what outbound paths they support.

How do we handle third parties that need to move data out for support or processing?

Put the third party on an approved channel with strong identity, least-privilege access, and time-bounded exceptions where needed. Keep a record of approvals, technical controls, and activity logs tied to that third party engagement.

What evidence is most persuasive in an assessment?

Assessors respond well to a tight chain: written standard, enforced configurations, and real operational records (change tickets, alerts, test results) that show the control works in production ².

Where does Daydream fit if we already have security tools?

Daydream helps you turn existing technical controls into audit-ready governance by mapping SC-7(10) to a control owner, an implementation procedure, and recurring evidence artifacts you can collect consistently ³.

Footnotes

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

2. NIST SP 800-53 Rev. 5

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