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By Vyrhak SATH · Founder, NAGASHIELD SECURITY5 minReviewed

How to write a network security policy

A network security policy defines how you segment, protect and monitor your networks. Here is what to include — segmentation, firewalls, remote access — with a free template.

Why network security still needs a policy

Even in a cloud-first world, the network is where access is granted or denied. A network security policy defines how you segment, protect and monitor connectivity so a foothold in one place does not become free movement everywhere.

What to include

  1. Scope — on-premises, cloud VPCs, and the boundaries between them.
  2. Segmentation — separate environments (production, development), and isolate sensitive systems.
  3. Perimeter controls — firewalls, security groups, default-deny rules and documented exceptions.
  4. Remote access — VPN or zero-trust access, always with MFA.
  5. Wireless — corporate vs guest separation, strong encryption (WPA2/WPA3).
  6. Monitoring — intrusion detection and traffic logging (links to your logging policy).
  7. Change control — firewall and network changes follow change management.

Common mistakes

  • Flat networks where one compromised host reaches everything.
  • Firewall rules that accumulate without review (allow-any creep).
  • Guest and corporate Wi-Fi on the same segment.

Framework alignment

Maps to ISO 27001:2022 Annex A 8.20–8.22 (network security, segregation), the SOC 2 criteria, and NIST CSF Protect (PR.AA / PR.IR).

Primary sources

  • ISO/IEC 27001:2022 — Annex A controls 8.20–8.22 (networks security, network services, segregation) (iso.org/standard/27001).
  • NIST Cybersecurity Framework — Protect function, Protective Technology (nist.gov/cyberframework).
  • ANSSI — guide d'hygiène informatique (cloisonnement et sécurisation du réseau) (ssi.gouv.fr).

Generate it in minutes

See a sample network security policy or generate yours free.

Frequently asked questions

What is network segmentation and why does it matter?

Segmentation splits a network into isolated zones so a compromise in one area cannot reach everything else. Putting servers, user devices, and guest traffic on separate segments limits lateral movement. Annex A 8.22 treats segregation of networks as a control to reduce the blast radius of an incident.

Does ISO 27001 require a network security policy?

Annex A 8.20 covers network security and 8.21 covers the security of network services. The standard expects networks to be managed and controlled to protect the information that flows over them, including documented rules for firewalls, remote access, and the services allowed between zones.

How often should firewall rules be reviewed?

At least annually, and after any significant network change. Reviews remove stale rules, tighten over-permissive entries, and confirm each rule still maps to a business need. Unreviewed rule sets accumulate risk silently, which is why auditors often ask for the date of your last firewall review.