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Interview question · Network Security & Protocols

How do attackers discover hosts, ports and services from the internet, and how do defenders find and shrink that exposure first?

The whole IPv4 internet is scanned many times a day. If a service answers, assume someone has already catalogued it.

easyEssentialNewPreparation tags: Palo Alto Networks, CrowdStrike, CloudflareUpdated Nov 2026

The whole IPv4 internet is scanned many times a day. If a service answers, assume someone has already catalogued it.

Make your first attempt

What would you say before reading the answer?

  1. 01 State the assumptions your answer depends on.
  2. 02 Explain the mechanism and choose a control.
  3. 03 Name a condition that would change your decision.

The worked answer includes an approach, scoring criteria and follow-up questions. Compare the reasoning with your own.

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What if · the follow-ups in this answer

The answer works through 6 follow-ups like an interviewer would

A company finds an old RDP server exposed to the internet that nobody remembers deploying.

  1. How does port scanning work?
  2. How do scanners identify services?
  3. Who is scanning?
  4. What do you do about this server?
  5. How do you find the next one first?
  6. How would you respond and prevent recurrence?

Each rung has a nudge, a model answer, the principle that carries over and the weak answer to avoid. Premium opens every answer and ladder.

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