The idea behind the defense in-depth is to defend a system against attacks by layering independent methods of defense and providing redundancy in case of a security control failure or vulnerability exploit.

The necessity of these layering approach is explained clearly by the Swiss Cheese Model: since no layer can be 100% secure, if we overlap different layer we can possible reduce the chance of an hole going all the way through.

Swiss Cheese security Model

The five functions of the NIST Cybersecurity framework :

Identify

Protect

Detect

Respond

Recover

There are multiple AWS services that can be used in combination at different levels to build secure Multi-Tier Applications:

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Let's have a look.