41. Session Hijacking – Tokens, Cookies and Defence

41.5 Network Sniffing of Sessions – Host-Only Concepts

By Ravindra Bagale Last updated: 15 October 2026

On a switched LAN, casual sniffing is harder than old hubs – but open Wi-Fi, misconfigured mirror ports, compromised routers, and MITM themes still teach why cleartext cookies die.

Lab-safe learning:

Wireshark / tcpdump on host-only interface while your lab browser talks HTTP to your PHP VM
See Cookie: headers in clear HTTP; contrast with TLS (payload encrypted)
Blue push: HTTPS + HSTS (Strict-Transport-Security) so browsers refuse downgrade

# Kali host-only – capture ONLY your lab subnet traffic (example interface name varies)
# sudo tcpdump -i eth1 -n host 192.168.56.40 and port 80 -w /tmp/lab-http.pcap
# Then open pcap in Wireshark; filter: http.cookie || http.set_cookie
# Never capture on bridged café Wi-Fi hunting strangers

Red team (attacker) does	Blue team (defender) detects / stops
Captures HTTP Cookie on open Wi-Fi / MITM lab	HTTPS + HSTS; Secure cookies; VPN on untrusted nets
SSL-strip / downgrade themes (awareness)	HSTS preload where appropriate; no HTTP links to auth
Compromises home router to sniff LAN	Router hardening; segment IoT; update firmware

Ravindra Bagale's Tip

Students run Wireshark on college Wi-Fi and call it "research" – a legal and ethical red flag. Only host-only lab VM traffic. Interview: "I demonstrate cookie exposure on my lab HTTP app, then enforce HTTPS." Now let's move on.

Lab

Start tcpdump/Wireshark on Kali toward 192.168.56.40:80 only. Login on weak HTTP PHP app. Confirm Cookie visible. Switch lab app to HTTPS (self-signed), re-login, confirm payload not readable as clear Cookie in same way. Screenshot ethics note in lab book.

Extended teaching notes

Why this lesson matters

Web flaws stay in the OWASP Top 10 because real apps still ship them. Your job is not to collect tool screenshots. It is to prevent and fix the class of bug on systems you own.

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.

Real examples

Global: injection and XSS still appear in breach reports and bug bounties every year. Indian company (sample): a Bengaluru SaaS team maps each OWASP item to a CI check or a code-review question so new code cannot silently reintroduce it.

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)

Write the lesson title, date and the exact lab target you are allowed to use.
List three owned systems (VMs, apps, or cloud accounts) where this lesson applies.
Run one safe check from the lesson on a lab system only. Paste the command and output.
Write a two-sentence fix you would give a teammate.
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.