ANSSI — ReCyF: Microsegmentation as a key NIS 2 control

Excerpt — On March 17, 2026, ANSSI released the Référentiel Cyber France (ReCyF), an operational guide to NIS 2 security measures. Focus: network microsegmentation, a concrete control to reduce intrusion impact and evidence compliance.

Key facts

On March 17, 2026, ANSSI published the Référentiel Cyber France (ReCyF), working version 2.5, translating NIS 2 obligations into concrete, measurable security objectives. The agency confirms that ReCyF lists expected technical, organizational, and operational measures, and provides support resources (framework comparator, tooling). For organizations operating in France—and more broadly, for any EU entity seeking an operational NIS 2 framework—ReCyF now serves as a practical compass to decide what to deploy and how to prove it. See ANSSI’s announcement and dedicated page: ANSSI — NIS 2 and press release 03/17/2026.

Among the flagship measures, network segmentation is emphasized: the goal is to limit lateral propagation after compromise, isolate sensitive environments (privileged accounts, critical systems, personal data), and enforce fine-grained access controls between zones. In the context of recent attacks (advanced BEC, dual‑channel, sophisticated phishing campaigns), segmentation becomes the safety net preventing a “peripheral” incident from escalating into a major crisis. See the trend analysis: Computer Weekly — BEC “dual‑channel”.

The applicable legal framework

- NIS 2, Article 21: duty to implement “appropriate and proportionate technical, operational and organizational measures” for risk management, including network security, access management, business continuity, and incident management. ReCyF clarifies what is expected in France and serves as an operational reference for audits/inspections. Sources: ANSSI — NIS 2.

- ISO/IEC 27001:2022, Annex A (control A.8.20 “Network security”): require architectures and mechanisms to protect confidentiality, integrity, and availability across networks—logical/physical segmentation, filtering, monitoring, hardening of inter‑zone flows. This standard provides a robust, internationally recognized evidence base for NIS 2 controls.

For Luxembourg stakeholders: although ReCyF is French, it is immediately usable alongside local resources (ILR) to demonstrate that “appropriate measures” under NIS 2 are documented, implemented, and audited. Luxembourg (ILR) and EU (ENISA) authorities stress the ability to prove effective implementation and risk control. A helpful resource to frame NIS 2 in Luxembourg: ILR — Security measures and supervision under NIS 2.

The technical solution to deploy: network microsegmentation

What is it for? Microsegmentation splits the network into small trust zones, each with minimal access policies (ZTA/Zero Trust “deny by default”). Objective: prevent lateral movement after initial compromise (endpoint, email, VPN, exposed app), contain the attack within a micro‑zone, preserve sensitive environments (AD, storage arrays, ERP, healthcare, payments), and facilitate investigation.

How does it work in practice?

• Inventory and flow mapping (assets, application dependencies, admin paths)—ISO 27001 A.5/A.8.20 prerequisite.
• Define zones (users, servers, OT/IoT, prod/preprod/dev, personal data, critical systems) and inter‑zone access policies (deny by default, least privilege).
• Enforcement controls: distributed firewalls (host/hypervisor), ACL/L3‑L7, EDR/XDR micro‑agents for enforcement, application access proxies, and strong authentication for admin flows (MFA, bastion/PAM).
• Continuous monitoring: log inter‑zone connections (NetFlow, eBPF, FW logs) to a SIEM; alert on deviations (SOAR) and conduct periodic policy reviews.
• Evidence: flow matrices, applicable rules, test reports (tabletop + technical tests), indicators (unjustified block rate, exceptions, remediation lead times).

Reference standards: ISO/IEC 27001:2022 (Annex A.8.20 Network; A.5.9 Inventory), NIST CSF 2.0 (PR.AC, PR.DS, DE.AE), CIS Controls v8 (CPS 12: Network Infrastructure Management; CPS 13: Network Monitoring and Defense). This approach aligns with ReCyF objectives on network protection, privileged access, and monitoring.

How Luxgap delivers

1) Targeted “flows and zones” assessment (2–4 weeks): our outsourced CISO/DPO consultants perform the application inventory, dependency mapping, and propose prioritized zones/inter‑zones (criteria: personal data, business criticality, exposure, privileges). Deliverables: “as‑is” flow matrix, “to‑be” model, candidate policies and rules.

2) Enforcement pilot: with your network/security team, we enable microsegmentation on a restricted scope (e.g., bastions + AD + ERP) in “observe”, then in “enforce”. Our managed SOC monitors logs 24/7 (distributed FW, EDR/XDR, NetFlow) and tunes rules via SOAR playbooks to avoid blocking false positives.

3) Governance and evidence: our ISO 27001 governance (Lead Implementer/Auditor) structures policies, exceptions, quarterly reviews, and KPIs; we align deliverables to NIS 2 (Art. 21) and ReCyF requirements, pre‑assembling expected audit artifacts (maps, policies, logs, test reports, admin entitlements).

Real‑world case in Luxembourg or the EU

A financial services company operating in Luxembourg (NIS 2 important entity) segmented into 8 zones (office IT, admins, app servers, sensitive databases, document management, critical SaaS, DR/backup, third‑party access). In 6 weeks: flow mapping, deny‑by‑default between sensitive zones, bastion + MFA for admins, blocking risky lateral protocols (unjustified SMB/RDP), logs to SIEM. Outcomes: 70% reduction in identified lateral paths, mean isolation time for a compromised workstation cut from hours to minutes, and a NIS 2 evidence pack ready for ILR (measures, logs, tests), leveraging equivalent ReCyF objectives for control traceability.

First concrete steps

1. Identify the “crown jewels”: list critical systems/data (including sensitive personal data) and privileged accounts; validate with business leadership.
2. Trace flows: enable NetFlow/eBPF/EDR “network visibility” on a pilot scope (e.g., ERP + AD) for 2 weeks; produce an “as‑is” matrix.
3. Define 4–6 priority zones with simple rules (allow: strictly necessary services; block the rest). Document “who can talk to whom”.
4. Set up an administration bastion with phishing‑resistant MFA and no direct RDP/SSH; log all sessions.
5. Feed logs to SIEM/SOC and establish a monthly review of exceptions and incidents; retain evidence for your NIS 2/ISO 27001 audits.

Official sources

• ANSSI — The NIS 2 directive (ReCyF publication, March 17, 2026)
• ANSSI — NIS 2: ANSSI strengthens its support (ReCyF, resources and tools)
• ILR (Luxembourg) — Security measures and supervision under NIS 2 (Art. 21)
• Computer Weekly — “Dual‑channel” BEC in 2026 (attack trend, news context)

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