Defense in depth is a familiar security strategy to anyone who’s been the cybersecurity industry for more than a few months. Defense in depth uses a layered approach to protect networks and systems from breaches. It relies on multiple lines of defense — or layers of security controls — to provide redundancy in the event that one defense fails or a vulnerability is exploited.
In a traditional, linear network, for example, defenses were implemented in a line: external firewall connected to filtering router connected to internal firewall. Two-factor authentication could be another layer of control.
A linear defense-in-depth strategy has been effective for systems that were not mobile and where data was more contained — where, for example, employees only connected to the internet from their desktop computers at the office. But over time, the scope of where we interact with the internet and store our data has expanded considerably. We carry our tablets and smartphones everywhere and have full access to corporate data and services. Furthermore, much of our workloads now reside in the cloud, and we share these virtual workspaces with our partners.
Is Defense in Depth Dead?
Defense in depth is not dead. In fact, it’s more important than ever. We still need layers of protection, but how we think about architecting those layers is due for a refresh. A single, linear model is not suited to most modern use cases. In today’s world of mobility and cloud, we need multiple types of layers for shifting use cases. What works on-premises may not be available in the cloud. How you secure access and data on a mobile device is, by nature, different from the on-premises desktop and server.
What we need now is a flexible, orbital approach to defense in depth that provides protection no matter where the data resides, whether it be in the cloud, on a mobile device or in an Internet of Things (IoT) sensor. Total, 360-degree, orbital protection requires an understanding of what controls are available and effective based on a number of factors, including type of device, user characteristics, data sensitivity and physical location.
Orbital Defense and the Human Immune System
In orbital defense in depth, devices and sensors create an interconnected set of layers that can communicate and share intelligence about system health and potential threats. The human body also uses multiple layers of defense against microorganisms such as viruses and bacteria. The skin acts as the first line of defense against these potential invaders because it is not very penetrable. Our airways are another possible route for viruses and bacteria to enter the body. We can’t close them off, but we do have additional lines of defense in our respiratory system. Tiny hairs trap organisms before they can reach the very penetrable mucous membranes that line our respiratory system, and coughs and sneezes can expel potential invaders.
In the digital security immune system, this need for flexibility and an orbital approach can be applied to defense in depth because not all layers are needed or available for all use cases. For example, full packet capture and system logs may not be available for workloads in public clouds, and biometric identification is available on most modern mobile devices, but is not as common on laptops or desktops.
The Power of Intelligence and Communication
Additionally, linear defense-in-depth architecture does not address the benefits of communication between layers or among systems in the same layer. One of the reasons the human immune system is so powerful is because its organs and cells work together through a sophisticated communication network. When an invader is detected, white blood cells get the alert and head to the site to destroy the pathogens. T cells cluster to share information about pathogens, “which in turn helps the immune system mount a coordinated response,” according to the University of California San Francisco.
The security immune system is an advancement over traditional, linear defense in depth because the layers can be applied by use case and they can communicate with each other. For example, if the security operations center (SOC) analytics tool detects unwanted traffic from an external device, the firewall can be alerted to block access from that device.
Or if a database monitoring tool flags activity as suspicious, it can share it with a user behavior analytics (UBA) tool. Using this information from another source, the UBA may have enough context to determine that the database activity is malicious and communicate this back to the database tool so the user or activity is blocked. These are just two examples of how a security immune system takes an integrated, orbital approach to the familiar layers of defense in depth.