Multiple layers of security (physical, technical, administrative).

Defense in depth is a strategy that involves using multiple layers of security to protect a system. If one layer is bypassed, the attacker still has to deal with additional layers of protection. For example, you might have firewalls, encryption, access control, intrusion detection systems, etc. This ensures that even if one defense is compromised, others are in place to continue protecting the system. An organization should have multiple security controls that address risks and threats in different ways. One example of a security control is multi-factor authentication, or MFA, which requires users to take an additional step beyond simply entering their username and password to gain access to an application. Other controls include firewalls, intrusion detection systems, and permission settings that can be used to create multiple points of defense, a threat actor must get through to breach an organization

  1. Perimeter layer, ****like authentication systems that validate user access
  2. Network layer, ****which is made up of technologies like network firewalls and others
  3. Endpoint layer, ****which describes devices on a network, like laptops, desktops, or servers
  4. Application layer, ****which involves the software that users interact with
  5. Data layer, which includes any information that’s stored, in transit, or in use

Defense in depth = layered controls so a single failure doesn’t expose the system.

Mental model

Think in 3 axes:

Defense in depth = all three at every layer.

Common mistakes