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Chapter 5: Amazon EC2 (Elastic Compute Cloud)

Interview Questions

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These EC2 questions are almost always asked in interviews. Don't learn the answers by heart – remember our the Amul-style dairy lab and answer in your own words; then the answer will sound confident on its own.

Q1. What is an AMI?
An Amazon Machine Image is a template containing the OS, software and configuration (backed by EBS snapshots) used to launch EC2 instances.
Q2. What is a security group? Is it stateful?
A virtual firewall at the instance/ENI level with allow rules for inbound and outbound traffic. It is stateful — return traffic for an allowed connection is automatically allowed.
Q3. What is the difference between stopping and terminating an instance?
Stop shuts it down and keeps the EBS root volume (auto public IP is released, EBS still billed). Terminate deletes the instance permanently and, by default, its root volume.
Q4. Explain EC2 pricing models.
On-Demand (pay per second, no commitment), Savings Plans and Reserved Instances (commitment for big discounts), Spot (spare capacity, up to ~90% off, can be interrupted), Dedicated Hosts/Instances (physical isolation).
Q5. How do you connect to a Linux EC2 instance from Windows?
Using the built-in OpenSSH client (ssh -i key.pem user@IP after fixing key permissions with icacls), PuTTY with a .ppk key, MobaXterm, EC2 Instance Connect or Session Manager.
Q6. What is user data?
A script passed at launch that runs automatically (as root, via cloud-init) on the first boot — used to install packages or configure the server.
Q7. What is the instance metadata service?
An endpoint at 169.254.169.254 inside each instance that returns metadata like instance ID, IPs, AZ and IAM role credentials. IMDSv2 requires a session token.

Extended teaching notes

Why this lesson matters

Cloud security is mostly IAM, network exposure, logging and secure defaults. The shared responsibility model means the provider patches the metal; you patch what you configure.

  • No public databases or public admin panels.
  • Roles / OIDC instead of long-lived access keys.
  • CloudTrail / Activity Logs / Audit Logs on and retained.
  • S3/Blob/GCS: Block Public Access; encrypt; least privilege.

Mini case study

Suppose we are on a purple-team exercise for an Indian mid-size company (sample data). Red notes a technique from this lesson against a lab clone. Blue must show the control that stops it, the log that would have fired, and the ticket that hardens production. That is the standard this course trains you for.

Defender's worksheet (do this today)

  1. Write the lesson title, date and the exact lab target you are allowed to use.
  2. List three owned systems (VMs, apps, or cloud accounts) where this lesson applies.
  3. Run one safe check from the lesson on a lab system only. Paste the command and output.
  4. Write a two-sentence fix you would give a teammate.
  5. Name one related public advisory (CERT-In, CISA, NVD, or a vendor bulletin) with its date.

Indian workplace (sample data)

Suppose we are a junior analyst at Infosys, TCS, Wipro or a fintech SOC in Bengaluru/Pune. Turn this lesson into one checklist item with an owner, a due date and a place to store evidence (ticket + screenshot).

Global practice

Compare your notes with OWASP, CIS Benchmarks, NIST CSF/IR guidance or a cloud Well-Architected security question. Write five lines on what overlaps.

Everyday analogy

Explain the risk and the fix to a family member without jargon. If they can repeat the warning, you understand it well enough to teach juniors.

Key terms

  • Control: a safeguard (patch, config, process, detection).
  • Finding: a weakness backed by evidence.
  • Remediation: the fix plus how you verified it.
  • Scope: systems you have written permission to touch.
  • Least privilege: only the access the task needs.
  • Defence in depth: several layers so one failure does not end the story.

Common mistakes

  • Skipping written permission "just for a quick scan".
  • Practising on hostel, office or public targets without authorisation.
  • Collecting tool output without writing the fix.
  • Copying attack steps onto production to "verify". Defenders verify with versions, configs and patches.
  • Publishing screenshots that contain secrets, cookies or internal hostnames.

Recap

  • Evidence, fix, owner, date.
  • Own lab only.
  • Fix > spectacle.