The ISO 27001 standard, which aims to make information security a corporate culture, offers various control clauses to ensure the security of technical infrastructure. One of the most dynamic and critical of these controls is network security. In particular, the technological controls under Annex A of the current version of the ISO 27001 standard (specifically security of networks, security of network services, and network segmentation) define in detail how companies should protect their network infrastructure.
To fully ensure network security and successfully pass audits, the correct configuration of firewall and virtual private network (VPN) technologies is of vital importance.
What are ISO 27001 Network Security Controls?
The ISO 27001 standard does not view network security merely as a hardware installation; it treats it as a holistic architecture supported by policies, processes, and continuous monitoring mechanisms. The main expectations of the standard regarding network security are as follows:
- Management and Control of Networks: Authorization of all devices on the network, keeping the network topology up to date, and controlling network traffic.
- Security of Network Services: Ensuring the security of network services such as DNS, DHCP, and defining security conditions in contracts made with service providers.
- Network Segmentation: Isolation of critical systems from user networks and the outside world (VLAN and DMZ configurations).
ISO 27001 Requirements in Firewall Management
A firewall is your first and strongest line of defense between your network and the outside world. For ISO 27001 compliance, firewall management is not just about positioning the device; the following processes must also be operated:
1. Regular Rule Review
Access rules on the firewall can become complex over time and create security vulnerabilities. ISO 27001 requires rules to be reviewed at regular intervals (e.g., every 3 or 6 months) and rules that are no longer needed to be deleted.
2. Change Management
Every rule change made on the firewall must be linked to a request process. The answers to the questions "Who, why, and with what authority opened this rule?" must be recorded and presented to auditors.
3. Logging and Monitoring
All traffic on the firewall, blocked connections, and administrator logins must be logged. These logs are of critical importance for the detection and analysis of cyber attacks. Enterprise firewall solutions such as Fortinet, Palo Alto, or Cisco have advanced reporting features to meet these requirements.
Remote Work and VPN Security
With remote and hybrid working models becoming the standard, the security of connections made to the company network from the outside has become one of the most examined topics in ISO 27001 audits. The following security measures are mandatory for VPN (Virtual Private Network) connections:
- Multi-Factor Authentication (MFA): VPN connections made with only a username and password are no longer considered secure. A second verification layer (MFA) such as SMS, mobile approval, or OTP must be used in VPN access.
- Strong Encryption Protocols: Modern and strong encryption standards such as AES-256 should be preferred instead of weak encryption algorithms in VPN tunnels.
- Keeping Access Records: Who connected to the VPN, from which IP address, when, and which resources they accessed on the network must be logged in detail.
Implementing Network Security Controls
Creating an ISO 27001 compliant network architecture requires both hardware investment and expertise. You can benefit from our Hardware and Software Solutions services for the procurement of network devices your organization needs.
To configure these procured devices in a secure and compliant manner that will pass audits, receiving professional Network Security, Firewall and IDS/IPS Solutions consulting will ensure that the process is completed smoothly.
Additionally, you can review our ISO 27001 Risk Assessment guide for risk analyses that need to be done before starting your network security processes. You can browse our article What is ISO 27001? to learn about the general structure of the standard, and benefit from our FortiGate VPN Connection Issue guide to resolve technical problems that may be experienced in VPN connections.
To make your company's network infrastructure compliant with ISO 27001 standards, optimize your firewall rules, and implement secure VPN solutions, please contact us.
Frequently Asked Questions
Which firewall brand should we choose for ISO 27001?
The ISO 27001 standard does not mandate a specific brand or manufacturer. The important thing is that the firewall you choose has central management, detailed logging, IPS/IDS (Intrusion Detection and Prevention), and strong encryption capabilities. Established enterprise brands such as Fortinet (FortiGate), Palo Alto, and Sophos provide convenience in audit processes.
Is MFA (Multi-Factor Authentication) mandatory for VPN connections?
Yes, in the current version of ISO 27001, the use of MFA for the security of remote access is a critical control clause. Auditors specifically check whether MFA is active in all administrative and user connections made to the company network from the outside.
How long should we keep firewall logs?
In line with legal regulations and ISO 27001 requirements, it is recommended to store firewall and network access logs securely and immutably (preferably timestamped) for at least 2 years.
Conclusion
Network security is the most dynamic part of the ISO 27001 Information Security Management System. A correctly configured firewall and secure VPN infrastructure increase your company's resilience against cyber threats while strengthening your hand in legal compliance and certification processes. Remember, network security is not a one-time installation, but a living process that needs to be constantly monitored and optimized.
