Imagine you are building your house, what do you start with - first of all you will secure your land area from trespassers with a boundary wall. You will probably also add a entry-point to allow people who are supposed to enter and work in the property.
Once the property is secured and marked, you will start designing the master plan of your house - no. of rooms, their types, passages etc. You will have to ensure there is seamless connectivity across the house at the same time it's secured from unwanted elements.
Building software infrastructure is similar, after all its the house where your potential best selling software will be deployed.
One of the critical strategies in achieving this is through network segregation, a practice that plays a pivotal role in maintaining ISO 27001 compliance. ISO 27001 is an internationally recognised standard that provides a framework for an Information
Security Management System (ISMS), helping organisations to systematically manage their information security risks. Network segregation, a key component of this framework, is essential for mitigating risks, protecting data, and ensuring compliance.
Understanding Network Segregation:
To secure connectivity Network should be segregated or subnetted with respect to incoming and outgoing access.
As in the house design example above, you have your living room accessible to all incoming people, bedroom is private to you, kitchen is visible to your guests however operated by you. Likewise identify the privacy layers in your network -
Is it Public , allowing ingress traffic from outside, or Private that is no incoming and outgoing internet access or is it Protected by allowing only outgoing access to internet.
Network privacy can be achieved via VPCs and subnets if you are hosted on cloud or through VLAN and DMZs if you are on premise and on legacy systems. You should have VPCs over classic or dynamic network.
Configurations must be logically segregated or tiered with respect to usage (e.g. per product or customer).
Firewall rules must be adapted per tier/subnet.
If necessary segregate virtual machines and appliances to dedicated hardware.
Always keep separate networks for production and non-production.
Network segregation, also known as network segmentation, involves dividing a network into smaller, distinct subnetworks or segments. Each of these segments operates independently, with limited or controlled communication between them. This approach restricts unauthorised access, minimises the attack surface, and confines any potential breaches to specific network segments, preventing them from spreading across the entire network.
The Role of Network Segregation in ISO 27001:
ISO 27001 emphasises the importance of implementing security controls to protect the confidentiality, integrity, and availability of information. Network segregation directly aligns with these principles by enforcing boundaries within the network and controlling access to sensitive data.
1. Risk Mitigation
One of the primary goals of ISO 27001 is to reduce the risk of security incidents. Network segregation helps achieve this by isolating critical systems and sensitive information from less secure areas of the network. For instance, an organisation may segment its network into different zones, such as a demilitarised zone (DMZ), internal network, and restricted network. The DMZ might host public-facing services, while the internal network contains day-to-day operational systems. By segregating these areas, even if a cyberattack compromises the DMZ, the attacker would face significant barriers in reaching the internal or restricted networks.
2. Access Control
ISO 27001 requires organisations to implement strong access control measures. Network segregation is instrumental in enforcing these controls by ensuring that users and systems can only access the network segments they are authorised to. For example, employees in the finance department might only have access to the financial systems segment, while the HR department can only access the HR systems segment. This not only limits the risk of unauthorised access but also helps in monitoring and auditing access, making it easier to detect and respond to suspicious activities.
3. Compliance with Legal and Regulatory Requirements
Many industries are subject to strict legal and regulatory requirements regarding data protection. Network segregation can help organisations meet these requirements by ensuring that sensitive data, such as personal identifiable information (PII), is stored and processed in isolated segments with enhanced security controls. This is particularly important in sectors like healthcare, finance, and government, where non-compliance can result in significant penalties and reputation damage.
4. Incident Response and Recovery
In the event of a security breach, the ability to contain and mitigate the damage is crucial. Network segregation aids in this process by limiting the spread of malware or unauthorised access to only the affected segment. This containment strategy allows organisations to respond to incidents more effectively and recover faster. For instance, if a ransomware attack targets a specific segment, the organisation can isolate that segment, preventing the malware from spreading to other parts of the network, thereby preserving the integrity of critical systems and data.
5. Enhanced Monitoring and Auditing
Network segregation facilitates more granular monitoring and auditing of network traffic. By segmenting the network, organisations can implement tailored monitoring solutions for each segment, making it easier to detect unusual or malicious activities. This level of detail is essential for maintaining ISO 27001 compliance, as it enables organisations to demonstrate that they have implemented effective controls and are actively monitoring their network for potential security threats.
Best Practices for Implementing Network Segregation
While the concept of network segregation is straightforward, its implementation requires careful planning and execution to align with ISO 27001 standards.
1. Define Clear Segmentation Policies
Organisations should start by defining clear segmentation policies that outline how their network will be divided and what security controls will be applied to each segment. These policies should be based on the organisation’s risk assessment and should consider factors such as the sensitivity of the data, the criticality of the systems, and the potential impact of a security breach.
2. Use Firewalls and Access Control Lists (ACLs)
Firewalls and ACLs are essential tools for enforcing network segregation. Firewalls can be used to control traffic between segments, ensuring that only authorised communication is allowed. ACLs can be applied to routers and switches to further restrict access at the network layer, preventing unauthorised devices from accessing sensitive segments.
3. Implement VLANs
Virtual Local Area Networks (VLANs) are a common technique for network segregation. VLANs allow organisations to create logically separate networks on the same physical infrastructure, providing a flexible and cost-effective way to segment the network. Each VLAN can have its own security policies, ensuring that sensitive data and systems are adequately protected.
4. Regularly Review and Update Segmentation
Network segregation is not a set-and-forget solution. Organisations must regularly review and update their segmentation policies and controls to ensure they remain effective. This includes conducting regular penetration testing, reviewing access logs, and updating firewalls and ACLs to address emerging threats and changes in the organisation’s network architecture.
Conclusion:
In the context of ISO 27001 compliance, network segregation is a critical security control that helps organisations protect their sensitive information, reduce risks, and meet legal and regulatory requirements.
By implementing network segmentation, organisations can not only enhance their security posture but also demonstrate their commitment to maintaining a robust Information Security Management System.
As cyber threats continue to evolve, the importance of segregated networks in achieving ISO 27001 compliance will only grow, making it an essential consideration for any organisation seeking to safeguard its digital assets.
A robust infrastructure needs to have secure and seamless connectivity across all systems and services.
To secure connectivity Network should be segregated or subnetted with respect to incoming and outgoing access using Firewall Policies to secure perimeter. There should a Single Secure Entry point for traffic landing from internet.
For seamless connectivity Dedicated Private Links should be used for peer to peer connectivity and data transmission.
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