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8. Hosting a Static Website and Changing the Configuration

8.7 Changing the Port

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Also in the AWS course: this lesson is the same as 8.6 Task: run a site on a different port in the AWS course, which is the main version of this page.

Kadhi kadhi admin panel kiwa dusri site vegalya port var chalvavi lagte, udaharanartha 8081.

# Nginx: /etc/nginx/conf.d/admin.conf   (Ubuntu: sites-available + symlink)
server {
    listen 8081;
    server_name _;
    root /var/www/admin;
    index index.html;
}

# Apache (AL2023/CentOS): add to /etc/httpd/conf.d/admin.conf
Listen 8081
<VirtualHost *:8081>
    DocumentRoot /var/www/admin
    <Directory /var/www/admin>
        Require all granted
    </Directory>
</VirtualHost>

On Ubuntu Apache, put Listen 8081 in /etc/apache2/ports.conf (not in the vhost file). Then:

  1. Test and reload the web server.
  2. Check that it listens: sudo ss -tlnp | grep 8081.
  3. Security group: add an inbound rule Custom TCP 8081 (from My IP for admin pages).
  4. CentOS Stream 9: open firewalld if active (sudo firewall-cmd --permanent --add-port=8081/tcp && sudo firewall-cmd --reload) and allow the port in SELinux:
sudo semanage port -l | grep -w http_port_t              # ports web servers may bind to
sudo semanage port -a -t http_port_t -p tcp 8081          # add 8081 if not listed

Without the SELinux step, the service fails to start with bind() to 0.0.0.0:8081 failed (13: Permission denied).

Why this matters for security

Moving a service to a non-standard port is not security – Nmap finds port 8081 in seconds. Real protection is the security group source rule (My IP only for admin ports), authentication and HTTPS. Every extra open port is extra attack surface.

Ravindra Bagale's Tip

You changed the port, the config is correct, the service is running – and still the site doesn't open. The reason: you didn't allow the new port in the security group! Many students forget this step. Check both ss -tlnp on the server and the inbound rule in AWS.

Lab

Serve /var/www/admin on port 8081 with Nginx. Allow 8081 only from My IP in the security group and confirm it opens from your laptop but not from your phone's mobile data.

Extended teaching notes

Why this lesson matters

Use this lesson to strengthen systems you own: understand the risk, practise safely in a lab, then write and apply the fix.

Apply the fix across stacks

Same class of bug, same idea in every language.

Java / Spring Boot

Parameterise queries, encode output, CSRF tokens, limited Actuator, dependency scanning.

ASP.NET Core

EF Core / parameterised SQL, Razor encoding, HTTPS, Data Protection.

Node.js / Express

helmet, parameterised SQL, npm audit, avoid eval and shell concat.

Python / Django / Flask / FastAPI

ORM, autoescape, pip-audit, Bandit; never shell=True with user input.

PHP / Laravel

PDO/Eloquent, Blade escaping, composer audit.

Go / Ruby

database/sql placeholders / ActiveRecord; html/template / ERB escaping; govulncheck / Brakeman.

nginx / Apache / Tomcat

Hide versions, TLS, security headers, least-open ports.

MySQL / PostgreSQL / MongoDB / Redis

Private networks, auth on, least-privilege users, no 0.0.0.0/0.

AWS / Azure / GCP

Roles not long-lived keys, private data stores, cloud audit logs on.

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.