SI-8: Spam Protection

SI-8 is easy to “have” and surprisingly hard to “pass” in an assessment. Most organizations already run an email security gateway or cloud email filtering, but fail the requirement because the control is not mapped to the right boundaries, outbound flows are ignored, or there is no repeatable evidence that spam is detected and actioned across the defined system. SI-8 also tends to sprawl beyond email. “Unsolicited messages” can enter through web contact forms, collaboration invites, SMS/MMS gateways, ticketing systems, and third-party integrations that post messages into internal channels.

As a Compliance Officer, CCO, or GRC lead, your job is to make SI-8 auditable: identify the entry/exit points, confirm what mechanisms are in place at each point, define the organization’s required actions for suspected spam, and ensure operations can produce clean artifacts on demand. The fastest path is to treat SI-8 like a boundary-control problem, then write a short, testable procedure with named owners and recurring evidence. The control text is brief, but “system entry and exit points” creates a concrete scoping obligation you can operationalize. ¹

Regulatory text

Requirement excerpt: “Employ spam protection mechanisms at system entry and exit points to detect and act on unsolicited messages; and” ²

What the operator must do:

1. Employ mechanisms: You need technical controls (native or third-party) that perform spam detection.
2. Place them at entry and exit points: Controls must sit where messages cross the system boundary, inbound and outbound.
3. Detect and act: Detection alone is insufficient. Your configuration must enforce an action (block, quarantine, tag, rate-limit, rewrite, route for review, or allow with documented exception).

A practical test: if an assessor asks, “Show me where unsolicited messages enter and leave, and show me what happens to them,” you should be able to answer with a boundary diagram, a control map, and live configuration evidence. ²

Plain-English interpretation (what SI-8 expects)

SI-8 expects you to run spam filtering where messages come in and where messages go out, then make consistent decisions about what happens when something looks like spam. The assessment focus is typically:

• Coverage: are all relevant message paths protected, or only corporate email?
• Enforcement: is the system configured to actually block/quarantine/tag, or just “score” and log?
• Governance: can you show ownership, documented rules, exception handling, and evidence of operation? ²

Who it applies to (entity and operational context)

SI-8 is commonly applied in environments aligned to NIST SP 800-53, including:

• Federal information systems
• Contractor systems handling federal data ²

Operationally, it applies anywhere your “system” processes messaging that can be unsolicited. Typical in-scope components:

• Email: cloud email tenant, gateways, secure email relays, inbound MX, outbound smart hosts.
• Web and collaboration: web proxies, chat/collaboration tenants, conferencing invite flows, shared mailbox ingestion, ticketing/email-to-case.
• Third parties: marketing email services, helpdesk providers, managed email security, and any integration that posts messages into internal systems (treat them as third party entry/exit points you must control contractually and technically).

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

Step 1: Define the “system” boundary and message flows

Create a simple inventory of message entry/exit points:

• Inbound email entry (MX records → gateway → mailbox)
• Outbound email exit (mailbox → relay/gateway → internet)
• Inbound web/contact form submissions (WAF/app → ticketing/CRM)
• Collaboration ingress (external guests, federation, inbound invites)
• Any third-party message injection (APIs, connectors, forwarding rules)

Deliverable: a one-page “Messaging Flow Map” that names systems, owners, and enforcement points.

Step 2: Select and document spam protection mechanisms at each choke point

For each entry/exit point, record:

• Control mechanism (native feature or third-party tool)
• What it detects (spam/phishing/bulk/graymail, as defined by your policy)
• What actions it can take (block/quarantine/tag/route/allow)
• Logging and alerting locations

Keep this in a control register so SI-8 is not “owned” only by email admins.

Step 3: Define “act on unsolicited messages” as a policy decision table

Write a short decision table your operations team can implement:

Condition (example)	Required action	Notes / approvals
High-confidence spam	Quarantine or reject	End-user release rules defined
Suspected spam/graymail	Deliver with subject tag or move to junk	User training and reporting path
Outbound bulk/automated send	Rate-limit or require authenticated relay	Prevent reputation damage and abuse
False positive exception	Allow with documented exception	Time-bound exceptions and review

The key is auditability: actions must be configured and consistent, not ad hoc.

Step 4: Implement outbound coverage explicitly

Assessors regularly find inbound filtering but weak outbound controls. Confirm:

• Outbound mail routes through a controlled relay/gateway.
• Sender authentication and relay permissions are restricted.
• Outbound spam/bulk anomalies trigger action (hold, block, or alert).

If outbound is handled by a third party (e.g., marketing platform), document the boundary: what leaves your environment, where enforcement happens, and what evidence you can obtain from the third party.

Step 5: Establish tuning, exceptions, and change control

Spam controls require tuning. Define:

• Who can change policies, allowlists, blocklists, thresholds, and transport rules.
• How changes are requested/approved (ticket + approval).
• How you review false positives/negatives and feed improvements back into configuration.

This is where GRC can drive consistency: tie policy changes to change management artifacts.

Step 6: Build recurring evidence collection (assessment-ready)

Create an evidence checklist that operations can satisfy without custom work:

• Monthly exports or screenshots of key policy settings (inbound and outbound).
• Message trace samples showing spam disposition outcomes (blocked/quarantined/tagged).
• Reports from the spam protection console showing volume and actions taken.
• Exception register (allowlist entries, transport rule bypasses) with approvals.
• Incident tickets tied to spam campaigns and lessons learned.

Daydream fits naturally here by mapping SI-8 to a named control owner, a short implementation procedure, and a repeatable evidence bundle so you do not rebuild proof every audit cycle. ²

Required evidence and artifacts to retain

Aim to retain artifacts that prove coverage, configuration, and operation:

• Boundary/data flow diagram for message ingress/egress (system entry/exit points).
• Configuration evidence: gateway policy settings, tenant anti-spam settings, outbound relay routing, transport rules, allow/block lists.
• Operational logs/reports: message trace samples, quarantine logs, disposition reports.
• Change records: tickets/approvals for policy tuning and exceptions.
• Third-party artifacts (if applicable): SOC reports are helpful but not sufficient alone; also retain console exports, service reports, or contractual control commitments aligned to your entry/exit points.

Common exam/audit questions and hangups

Expect these questions:

• “List your system entry and exit points for messaging. How did you validate completeness?”
• “Show the configured actions for suspected spam. Where is quarantine configured?”
• “How do you handle outbound spam or compromised accounts sending bulk messages?”
• “Who can add allowlist entries or bypass rules, and where are approvals recorded?”
• “Show evidence the control operated over time, not just today.” ²

Hangups that slow teams down:

• No documented boundary for “system” and “entry/exit.”
• Evidence exists but is not packaged; admins can show screens live, but cannot produce artifacts on request.
• Exceptions live in inbox rules or ad hoc allowlists without approvals.

Frequent implementation mistakes and how to avoid them

1. Email-only scoping: If your environment ingests messages into ticketing, collaboration, or CRM, document those paths and controls. Fix by creating the Messaging Flow Map and assigning owners.
2. Inbound-only protection: Outbound flows matter. Fix by proving all outbound mail routes through an enforcement point and that you monitor outbound anomalies.
3. “Detect” without “act”: Logging a spam score is not an action. Fix by documenting and enforcing disposition outcomes.
4. Uncontrolled allowlists and bypass rules: These become permanent backdoors. Fix by time-bounding exceptions and routing changes through approvals and periodic review.
5. No operational evidence: A working tool does not equal a provable control. Fix by scheduling recurring exports/reports and storing them in your GRC evidence repository.

Enforcement context and risk implications

No public enforcement cases were provided in the source catalog for this requirement, so treat enforcement risk as indirect: SI-8 gaps are commonly cited as control weaknesses during assessments, and operationally they increase exposure to phishing, business email compromise precursors, malware delivery, and data loss via outbound abuse. Your strongest risk reduction comes from complete boundary coverage and enforced actions with monitored exceptions. ²

Practical 30/60/90-day execution plan

First 30 days (stabilize scope and ownership)

• Name the SI-8 control owner and technical implementers (email/collaboration/security operations).
• Produce the Messaging Flow Map for entry/exit points.
• Inventory existing spam mechanisms and identify coverage gaps (especially outbound and third-party injection paths).
• Define the decision table for “act on unsolicited messages,” including exception approval rules.

Next 60 days (close coverage gaps and make it auditable)

• Implement or route all inbound/outbound flows through enforcement points.
• Lock down who can change spam policies and allowlists; require tickets and approvals.
• Configure logging/reporting so you can export operational proof without custom queries.
• Stand up an exception register and periodic review cadence.

By 90 days (operate, tune, and package evidence)

• Run a tuning cycle: review false positives/negatives and document rule changes.
• Collect a full evidence bundle: configs, logs/reports, samples of dispositions, and change records.
• Dry-run common audit requests: “show me inbound and outbound disposition,” “show me exception approvals,” “show me continuous operation evidence.”
• In Daydream, map SI-8 to the procedure and recurring artifacts so evidence collection becomes routine rather than a scramble. ²

Frequently Asked Questions

Does SI-8 apply only to email?

No. Treat “unsolicited messages” as any message-based intake or delivery path in your system boundary, including ticketing ingestion, collaboration invites, and third-party connectors. Document each entry/exit point and the mechanism that detects and acts on spam. ²

What counts as “act on” spam?

“Act on” means an enforceable outcome configured in the control, such as rejecting, quarantining, tagging, routing for review, or rate-limiting. Decide actions in policy, implement them in configuration, and retain evidence that dispositions occur. ²

If a third party provides our email security, are we still responsible?

Yes. You can outsource operation, but you still need to show coverage at your entry/exit points and retain evidence from the provider (configs, reports, and exception/change records). Treat the provider as part of your control boundary. ²

How do we handle necessary allowlisting without breaking compliance?

Use a documented exception process with approvals, scope limits, and periodic review. Keep an exception register that ties each allowlist entry or bypass rule to a ticket and an owner. ²

What evidence is most persuasive to auditors for SI-8?

A boundary/flow diagram plus configuration exports and operational reports showing spam dispositions over time typically satisfies both design and operating effectiveness. Add change tickets for tuning and a controlled exception register to address common follow-ups. ²

We have strong phishing controls. Do we still need separate “spam” controls?

SI-8 is scoped to unsolicited messages, which overlaps with phishing but is not identical. If your tooling covers both spam and phishing at entry/exit points and enforces actions, document that mapping and show the specific anti-spam settings and dispositions. ²

Footnotes

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

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