Strengthening network security guide

Securing Network Boundaries

How do you control what you allow in and out of your network?

While network architectures become more dynamic, it remains vital to safeguard known boundaries to maintain control and reduce risk. These boundaries often exist between subnets, virtual networks, or security zones, and are common points where perimeter defences should be applied.

Firewalls are a key tool in enforcing these controls, allowing you to filter traffic between zones based on specific rules. Additionally, Domain Name System (DNS) infrastructure is a growing focus for security, since it plays a crucial role in routing network traffic and is a frequent target for attackers. Protecting DNS should be considered an integral part of your perimeter security strategy.

Firewall Rule Management

How do you manage what traffic is allowed or denied?

Firewalls, whether hardware or software – are fundamental to preventing unauthorised access to your network. They use sets of rules to control traffic, typically combining allow and deny rules.

• Allow rules permit traffic matching certain attributes, such as source or destination IP addresses, domains, ports, or applications.
• Deny rules block traffic based on known malicious sources or unwanted patterns.

Rules are generally processed from top to bottom, and the first matching rule determines whether traffic is allowed or denied. A best practice is to include a final “deny all” rule to block anything not explicitly permitted, reinforcing the principle of least privilege.

DNS Security

How do you protect the DNS infrastructure your network relies on?

DNS is critical for translating human-friendly domain names into IP addresses that computers use to communicate. Because almost all networks depend on DNS, securing it is essential. Key protections include:

• Controlling who can make changes to DNS records or servers
• Limiting the number of DNS queries to prevent abuse
• Using DNS Security Extensions (DNSSEC) to validate query responses
• Implementing deny lists of known malicious domains based on threat intelligence

Treating DNS as a core part of your security perimeter helps prevent attackers from redirecting or intercepting network traffic

Protecting Data in Transit

How do you protect data that traverses networks?

A core function of any network is to move data between devices and systems, which often involves sensitive information passing through infrastructure whose security cannot always be guaranteed. To reduce risk, it is essential to put controls in place that protect the confidentiality, integrity, and availability of data while it is in transit.

Encryption technologies, such as Transport Layer Security (TLS), help secure data by making it unreadable to anyone intercepting the communication. Additionally, using virtual private networks (VPNs) can create secure tunnels over untrusted networks (most often the internet), safeguarding data from eavesdropping or tampering.

Planning for secure data transmission should consider both internal and external traffic, ensuring appropriate protections are applied wherever sensitive data flows.

Virtual Private Networks (VPNs)

How do you secure access and connections from outside your controlled network?

VPNs create secure connections over untrusted networks, such as the internet, allowing remote users or systems to access your network safely. It is critical to maintain VPN software and appliances throughout their entire lifecycle, ensuring they are regularly updated and properly configured.

Failing to do so increases the risk that attackers might exploit vulnerabilities in your VPNs to gain unauthorised access to your network. Regular patching, strong authentication, and monitoring are essential to keep VPNs secure and reliable.

Protocol Security

Are the protocols you use appropriate?

The network protocols you support should be chosen with security and resilience in mind. Selecting protocols that have built-in security features helps reduce the chance of compromise and makes detecting malicious activity easier.

For example, using HTTPS instead of HTTP for web traffic ensures encryption of data in transit, protecting users and systems from interception or tampering. Similarly, prefer secure alternatives for other services wherever possible to maintain a robust security posture.

Security Monitoring

How do you detect if your network has been compromised?

An effective security monitoring function enables your organisation to identify unusual or unauthorised activity on your network before it causes significant harm. This means detecting behaviour that deviates from your organisation’s policies or normal usage patterns.

To ensure your monitoring is effective, you should:

• Clearly define what activities and threats you need to monitor for
• Collect and maintain the necessary logs for analysis
• Use tools that provide actionable insights rather than just raw data
• Develop the capability to detect signs of misuse or compromise promptly

Timely detection supports swift response, reducing the impact of any security incident.

Keeping Systems Secure and Up to Date

How do you keep your systems secure and up to date?

Installing the latest software updates is vital for maintaining security. You should establish a policy of applying updates as soon as they become available, ideally automating this process wherever possible. Cloud native security tools may do this for you.

Regular updates fix vulnerabilities that attackers might otherwise exploit to gain access to your network.While some exceptions may apply – such as safety-critical systems or operational technology – keeping most systems current should be your standard practice.

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