The Basics of Defence-in-Depth
Defence-in-depth is a cybersecurity strategy that employs multiple layers of protection to safeguard a business’s assets (employee, customer and partner data, etc).
If one of these layers is compromised, cybercriminals still have to penetrate all the other layers before successfully infiltrating your systems.
Put simply, it’s harder for an attacker to jump ten consecutive hurdles than it is for them to jump one.
For fans of history, think of how castles often had a moat, raisable drawbridges, outer walls, interior walls, and finally, a keep. This layered approach was as relevant then as it is now.
Why is Defence-in-Depth such an Important Strategy?
Nowadays, given the complexity and sophistication of modern cyberattacks, no single security solution can promise complete protection.
New attack methods are constantly being developed, zero-day vulnerabilities are common, with Google’s Threat Analysis Group claiming that 97 zero-day vulnerabilities were exploited in 2023, and human error is still the most common cause of data breaches.
By implementing a layered security model, businesses can address vulnerabilities at different levels, making it significantly harder for attackers to succeed.
In some cases, cybercriminals have been known to avoid targeting companies with complex defence-in-depth solutions because of the extra time and effort required to breach them, preferring to target companies with inferior cyber defence systems.
Common Layers in Defence-in-Depth Strategies
We would be here for hours if we tried to explain every possible layer of a defence-in-depth strategy, so we have picked a few common ones to focus on.
External AND Internal Network Security
Network security focuses on safeguarding the flow of data within your network. Since many cyberattacks use lateral movement and privilege escalation to scour your network for sensitive data, it is easily one of the most important aspects of any defence-in-depth strategy.
Most people focus their attention on external network security, which is a dangerous strategy that goes against the defence-in-depth philosophy in many ways.
The thinking behind this is that if we can stop people from getting past our external network, then we don’t need to worry.
The problem is that there are several ways for attackers to bypass external network security altogether (physical breaches, insider threats, etc).
So, it is important that you build up both your external AND internal network defences.
Tools like firewalls, intrusion detection and prevention systems (IDPS), and virtual private networks (VPNs) form a protective barrier around the network. Network segmentation and segregation are two very common internal network security strategies.
Don’t forget to conduct regular vulnerability assessments on your external and internal networks, and book at least one penetration test per year to ensure network vulnerabilities are found and fixed.
Physical Security
In some instances, physical security is the first layer of defence. It protects the hardware and infrastructure that store and process sensitive information by preventing unauthorised access to business premises.
Even the most advanced cybersecurity measures are ineffective if unauthorised individuals can physically access critical systems.
For example, a stolen server or an unlocked workstation can provide attackers with direct entry points into a network, bypassing all digital protections.
Physical security guards, CCTV, and controlled access barriers are common forms of physical security, but what shouldn’t be overlooked is culture. If you can foster a zero-trust, cyber-conscious culture, your employees can act as another layer of security.
Endpoint Protection
Moving on from physical security to physical devices, endpoints—such as desktops, laptops, mobile devices, and servers—are often the entry points for cyberattacks.
Endpoint protection solutions, including antivirus software, endpoint detection and response (EDR) tools, and patch management systems, protect these devices from malware, ransomware, and other threats.
Since employees frequently use endpoints to access critical systems, securing them helps prevent attackers from using compromised devices as gateways into the broader network.
Data Protection
Data protection is often the final layer of defence. Since the aim of most cyberattacks is to steal or delete sensitive data, this is usually your last chance at preventing disaster.
Some common data protection strategies include encryption, which ensures data remains unreadable even if intercepted, data loss prevention (DLP) tools, which prevent unauthorised data transfers, and regular backups, which ensure data can be restored if lost or corrupted.
By protecting data at rest, in transit, and in use, businesses can reduce the impact of breaches and maintain the confidentiality, integrity, and availability of their information.
Benefits of Deploying a Defence-in-Depth Strategy
Much like the possible layers of a defence-in-depth strategy, the benefits are numerous, and it would take hours to go through them all. So, here are a select few.
Comprehensive Protection Against a Wide Range of Threats
Defence-in-depth provides layered security, ensuring that no single vulnerability can compromise the entire system.
Put simply, different defensive layers address different potential threats—a holistic approach that reduces the likelihood of successful attacks, whether they come from external hackers, insider threats, or malware.
Enhanced Threat Detection and Response
When multiple layers of security exist, the likelihood of detecting threats significantly increases, ultimately improving one’s ability to respond appropriately.
Time is exceptionally valuable when it comes to cybersecurity. In the best-case scenario, early detection can prevent the attack altogether, but in cases where the attack is still successful, it can significantly reduce the reputational and financial damage caused.
Ensures Regulatory Compliance
Many industries are subject to strict regulatory requirements, such as GDPR, HIPAA, or PCI-DSS, which require robust data protection measures. By employing a defence-in-depth strategy, businesses can meet these strict regulatory requirements with relative ease.
Controls like encryption, access management, and audit trails enhance security and provide the documentation and safeguards needed to demonstrate compliance during audits or investigations.
Conclusion
By implementing a defence-in-depth cybersecurity strategy, you are giving your business the best possible chance of preventing, detecting and responding to cyberattacks.
This approach not only keeps your employee, customer, and partner data safe, but it also helps build brand trust, maintain regulatory compliance, and more.
A word of warning: perfect cybersecurity is not possible, so even companies with defence-in-depth cybersecurity measures can be on the receiving end of cyberattacks.
This is why it is imperative that you remain vigilant and conduct regular vulnerability assessments and at least one penetration test per year to ensure that there are no vulnerabilities.