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Clairos Learn

35 lessons · UNIX / Linux

Security administration

Identity, sudo boundaries, SSH hardening, firewall rules, and review notes.

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What you will practice

Security admin; SSH hardening; Firewall and incident review; Auth log review.

Use the worked examples when needed, then test your understanding without them.

  1. 01Security adminPractice security habits: identity, logs, firewall rules, and simulated sudo.Practice
  2. 02SSH hardeningRead training SSH settings and confirm safer defaults without connecting anywhere.Practice
  3. 03Firewall and incident reviewInspect firewall state, add a simulated rule, and write a short incident note.Practice
  4. 04Auth log reviewSearch training SSH activity for accepted and denied attempts.Practice
  5. 05Firewall baselineInspect and update simulated firewall rules with caution.Practice
  6. 06SSH config reviewVerify key SSH hardening settings.Practice
  7. 07Least privilege reviewInspect identity and simulated sudo boundaries.Practice
  8. 08Incident noteWrite a short lab incident note from log evidence.Practice
  9. 09Exposed servicesCompare listeners, firewall rules, and nginx config.Practice
  10. 10Web hardeningInspect training nginx API blocking and CSP headers.Practice
  11. 11Script trust reviewHash and compare a training deployment script before trusting it.Practice
  12. 12Log retention reviewReview log size and line counts before cleanup decisions.Practice
  13. 13Account hygieneReview training accounts and root presence safely.Practice
  14. 14Final incident reviewPull together logs, firewall state, and a final review note.Practice
  15. 15SSH dry runInspect SSH client configuration without connecting.Practice
  16. 16SSH key fingerprintRead a simulated key fingerprint.Practice
  17. 17SCP dry runUnderstand copy shape without network transfer.Practice
  18. 18Package security reviewInspect package metadata during a security review.Practice
  19. 19Auth config checkpointReview SSH, identity, firewall, and notes.Practice
  20. 20Hardening summarySummarize posture from logs, config, and service exposure.Practice
  21. 21SSH hardening deep reviewReview SSH config, key mode, and host identity.Practice
  22. 22Firewall listener reconcileMatch exposed ports to firewall policy.Practice
  23. 23Known host key contextReview SSH host identity without connecting.Practice
  24. 24Sudo boundary reviewConfirm sudo is limited to safe inspection.Practice
  25. 25Account inventory reviewInventory users, groups, and service accounts.Practice
  26. 26Package security deep reviewConnect package state to recent package logs.Practice
  27. 27Log redaction noteCapture evidence without copying more than needed.Practice
  28. 28Hardening header reviewInspect web security header config and static API blocking.Practice
  29. 29Service exposure noteWrite a short exposure review from listener evidence.Practice
  30. 30Security evidence checkpointTie identity, SSH, firewall, and logs into a review.Practice
  31. 31SSH client and server policyCompare resolved client settings with server authentication policy.Practice
  32. 32Known-hosts hygieneInspect stored host identities alongside a key fingerprint.Practice
  33. 33Exposed service inventoryCompare listeners, firewall policy, and enabled service units.Practice
  34. 34Privileged boundary reviewRead the simulated sudo boundary and verify the target service action is inspection-only.Practice
  35. 35Security administration bridgeCheckpoint SSH policy, identity, listeners, and firewall evidence.Practice