“Defense in Depth” is a foundational principle in ISA/IEC 62443, defined as:
“The application of multiple security countermeasures in a layered (stepwise) fashion to protect assets.”
(ISA/IEC 62443-1-1, Clause 3.2.65)
The objective is to reduce the probability that a single point of failure or vulnerability can be exploited to compromise the system. Layers may include physical security, network segmentation, authentication, intrusion detection, and endpoint protection.
From ISA/IEC 62443-3-3:
“Defense in depth should be employed to provide redundancy in security mechanisms. Each layer increases the security of the system and mitigates different types of threats.”
Incorrect Options:
A and B – Misinterpret the concept as technical complexity, rather than layered protection.
C – Refers to physical spacing, not a cybersecurity strategy.
[References:, ISA/IEC 62443-1-1:2007 – "Terminology, Concepts, and Models", ISA/IEC 62443-3-3:2013 – "System Security Requirements and Security Levels", ISA/IEC 62443 Study Guide, ===========, , ]
