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Capability Detail

Cybersecurity & Compliance

Cybersecurity services for buyers operating under NIST, Cybersecurity Maturity Model Certification (CMMC), and federal compliance frameworks. Microsoft Sentinel SIEM and the Microsoft Defender XDR family as the reference substrate. Assessment through continuous monitoring, with evidence and audit-response artifacts produced as first-class deliverables.

Microsoft Sentinel + Defender Reference Architecture · Substrate alternatives available where buyer environment dictates
At a glance
What this is
Cybersecurity services aligned to NIST 800-53, NIST 800-171, CMMC, and federal compliance frameworks. Microsoft Sentinel SIEM and Microsoft Defender XDR as reference substrate.
Who it’s for
Federal and regulated commercial buyers operating under audit obligations — including buyers on Azure Government, GCC, and GCC High regulated tenancy.
Reference architecture
Microsoft Sentinel (SIEM) · Microsoft Defender XDR family (endpoint, identity, cloud, productivity) · Microsoft Purview for data governance. Substrate alternatives available where buyer environment dictates.
Engagement model
Three-phase delivery — assessment → remediation → continuous monitoring. Evidence collection, control mapping, and audit-response artifacts produced as deliverables.

Overview

Compliance posture, not compliance theater

Regulated buyers do not need another checklist. They need an operational security posture that survives the audit, the incident response, and the next framework revision — and produces the evidence trail to prove it. The gap between "controls implemented" and "controls operating and evidenced" is where most regulated programs lose time, lose contracts, and absorb avoidable risk.

Cornerstone Systems Group delivers cybersecurity services aligned to NIST 800-53, NIST 800-171, CMMC, and the federal compliance framework family. Engagements deploy on the buyer's Microsoft tenancy using Microsoft Sentinel for SIEM and the Microsoft Defender XDR family for endpoint, identity, cloud, and productivity coverage. Evidence collection, control mapping, and audit-response artifacts are produced as deliverables — not as a downstream scramble when the audit window opens.

Reference Architecture

Microsoft Sentinel + Defender XDR

The reference architecture deploys Microsoft Sentinel as the SIEM and SOAR surface, with the Microsoft Defender XDR family — Defender for Cloud, Defender for Endpoint, Defender for Identity, and Defender for Office 365 — providing coverage across cloud workload, endpoint, identity, and productivity surfaces. Entra ID Conditional Access enforces identity-driven access policy. Microsoft Purview provides data loss prevention and insider-risk telemetry. Azure Policy and Defender for Cloud regulatory compliance dashboards generate the evidence trail for framework assessments.

Engagement deployment is compatible with Azure Government, GCC, and GCC High regulated tenancy where the buyer's classification posture requires it — operating within the buyer's certified envelope rather than asserting independent certification. Where the buyer operates non-Microsoft substrate, engagement proceeds with substrate-native SIEM, XDR, and policy tooling under the same delivery posture.

Delivery Model

Three-phase implementation

Phase 1

Assessment

Current-state inventory of identity, endpoint, cloud workload, and data surfaces. Control mapping to the applicable framework (NIST 800-53, NIST 800-171, CMMC Level 1 or 2, or buyer-specified equivalent). Gap analysis with prioritized remediation roadmap. Pre-assessment evidence baseline captured in tenant-resident artifacts.

Phase 2

Remediation

Control implementation across the Sentinel and Defender surfaces per the remediation roadmap. Conditional Access policy deployment. Logging, audit pipeline, and evidence capture hardened. System Security Plan (SSP), Plan of Action & Milestones (POA&M), and supporting artifacts authored to the format and detail level assessors require.

Phase 3

Continuous Monitoring

Operational handover of Sentinel detection logic, Defender response playbooks, and recurring assessment cadence to the buyer's security operations team. Continuous evidence pipeline for framework attestation. Incident-response runbook and tabletop scenario library transferred for sustainment.

Engagement Patterns

Where cybersecurity and compliance services earn their keep

Engagement patterns share a common shape: the buyer operates under a regulated framework with mandatory control implementation and evidence requirements, the security stack is Microsoft-aligned or becoming so, and the buyer needs the assessment, remediation, and sustainment posture documented to assessor or auditor standard.

  • Defense industrial base CMMC Level 2 readiness. DIB contractor preparing for CMMC Level 2 assessment requires gap analysis against the 110 NIST 800-171 controls, remediation on the Microsoft Sentinel and Defender substrate, and SSP / POA&M documentation in the format and detail level C3PAOs expect at Level 2 assessment. Engagement delivers tenant-resident evidence and audit-response artifacts rather than spreadsheet-based attestation.
  • Prime contractor sub-fleet CMMC uplift. Prime contractor with a portfolio of CMMC Level 1 subs requires coordinated Level 2 uplift across the fleet. CSG provides assessment, remediation roadmap, and Sentinel / Defender implementation per sub with consistent evidence-pipeline architecture across the portfolio.
  • Federal civilian agency Risk Management Framework (RMF) authorization support. Federal civilian agency or supporting contractor requires RMF (NIST SP 800-37) authorization package support for a new or re-authorizing system. CSG provides control implementation, SSP authoring, continuous monitoring strategy, and assessor-ready evidence on the agency's Azure Government or GCC High tenant.
  • Enterprise SIEM modernization on Microsoft Sentinel. Regulated enterprise running legacy SIEM tooling requires migration to Microsoft Sentinel with parity coverage, retention of detection logic, and zero gap in audit-log coverage during the cutover. Engagement delivers detection-logic migration, tuned analytics rules, and SOAR playbook portability for the buyer's security operations team.

Capability Summary

What the engagement delivers

  • Assessment, remediation, and continuous monitoring across the regulated framework family
  • Microsoft Sentinel SIEM and SOAR implementation
  • Microsoft Defender XDR coverage — Cloud, Endpoint, Identity, Office 365
  • Entra ID Conditional Access policy design and deployment
  • Microsoft Purview for DLP and insider-risk telemetry
  • SSP, POA&M, and audit-response artifacts in assessor-required format
  • Compatible with Azure Government, GCC, GCC High regulated tenancy (within buyer's certified envelope)
  • Senior workstream leadership; documentation-first delivery posture

Common Procurement Questions

What buyers ask about CSG cybersecurity and compliance engagements

  • Can CSG serve as a Cybersecurity Maturity Model Certification (CMMC) Third-Party Assessment Organization (C3PAO)?

    No. CSG is not a C3PAO and does not perform third-party CMMC assessments. CSG performs assessor-readiness work: gap analysis against the 110 NIST SP 800-171 controls, remediation on the buyer's Microsoft Sentinel and Defender substrate, and System Security Plan and Plan of Action and Milestones (POA&M) authoring in the format C3PAOs expect at the CMMC Level 2 assessment window. The buyer engages a separately authorized C3PAO for the formal assessment.

  • What does a CMMC Level 2 readiness engagement typically scope?

    A typical Level 2 readiness engagement scopes a Phase 1 assessment covering all 110 NIST SP 800-171 controls against the buyer's current Microsoft 365, Azure, and endpoint environment; a Phase 2 remediation roadmap with control-by-control owners, target completion dates, and Sentinel/Defender configuration deliverables; and a Phase 3 sustainment handoff with continuous-monitoring playbooks and recurring evidence-collection cadence. Total elapsed time is six to twelve months depending on the size of the gap inventory and the buyer's pace.

  • Can CSG support a Federal Risk Management Framework (RMF) Authorization to Operate (ATO) package?

    Yes. CSG supports RMF (NIST SP 800-37) authorization packages for federal civilian agencies and supporting contractors with control implementation against the applicable NIST SP 800-53 baseline, System Security Plan authoring, continuous monitoring strategy, and assessor-ready evidence on the agency's Azure Government or GCC High tenant. CSG does not issue the ATO; the agency Authorizing Official issues the ATO after assessor review.

  • Does CSG hold independent third-party certification under CMMC, FedRAMP, or ISO 27001?

    No. CSG does not currently hold independent third-party certification under CMMC, FedRAMP, or ISO 27001. CSG operates within the buyer's certified or authorized environment. Where the solicitation requires a certified subcontractor, CSG declines the prime role and surfaces the gap explicitly. See Government Acquisition for certification pathway status.

  • Can CSG perform a Supplier Performance Risk System (SPRS) self-assessment for a Defense Industrial Base (DIB) subcontractor?

    Yes. CSG performs the underlying NIST SP 800-171 self-assessment, produces the artifact set required for the buyer to submit an SPRS score, and authors the supporting System Security Plan and POA&M. The buyer submits the SPRS score through their own SPRS account; CSG does not submit on the buyer's behalf.

  • How does CSG handle engagements that span Microsoft and non-Microsoft tooling?

    The Microsoft Sentinel and Defender XDR substrate is the reference architecture, but the delivery posture (assessment, remediation, continuous monitoring, evidence-as-deliverable) is substrate-portable. Engagements that include legacy Security Information and Event Management (SIEM) tools, non-Microsoft endpoint detection and response, or third-party identity providers are scoped to integrate rather than replace. Substrate replacement is a separate engagement shape with its own scoping cycle.

Posture Note

What CSG does and does not assert

Cornerstone Systems Group delivers cybersecurity services aligned to the frameworks above and operates within the buyer's certified tenancy where required. CSG does not currently hold independent third-party certification under CMMC, Federal Risk and Authorization Management Program (FedRAMP), ISO 27001, or equivalent frameworks. Where a solicitation requires firm-level certification, CSG will surface this posture in the response framing and route accordingly. Certification pathway is documented on the Government Acquisition reference page.

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Scoping a CMMC assessment, planning an RMF authorization package, or evaluating a Microsoft Sentinel migration? Send a capability inquiry and we will respond within one business day.

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Reviewing procurement fit? See Government Acquisition for North American Industry Classification System (NAICS) coverage, SAM registration status, and contract-vehicle pursuit posture.