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Case A19DE5 · Network · L4 Advanced

Securing OT Networks

Practise as: Deep dive
  1. 01 Context
  2. 02 Mechanism
  3. 03 Lessons
Practise this card
What a strong answer covers

Try it out loud first. Then check yourself:

  1. Purdue model separates enterprise (L4-5), DMZ (L3.5), operations (L3) and control/field levels (L0-2)
  2. Industrial protocols like Modbus/TCP and DNP3 often lack authentication, so reachability equals control
  3. Use an IT/OT DMZ with jump hosts and historian replicas; no direct enterprise-to-PLC connections
  4. Passive monitoring (SPAN/TAP) is preferred since active scanning can crash fragile controllers
  5. Availability and safety come first; patch windows are rare, so compensating network controls dominate

If the interviewer pushes back

  • How did the attackers in the 2015 Ukraine grid incident cross from IT into OT?

cardosec draws a security topic and gives you a clock: explain it out loud with no notes, then see what you covered and what you missed. Free during early access.