Many people I know get easily overwhelmed when they talk about IT and data security. I want to share a model called defense in depth that I learned from my security courses at the SANS Institute. You need to create security layers around each of the following components in your IT environment. The onion approach could make it harder for intruders to go through multiple security controls before they finally reach their target your data. If your data security is too restrictive, your flexibility and ability to conduct business will be negatively affected.”]
Source: https://securityintelligence.com/data-security-defense-in-depth-the-onion-approach-to-it-security/