Digital Evidence & Chain of Custody

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📁 Digital Evidence & Chain of Custody

📘 1️⃣ What is Digital Evidence?

Digital Evidence is any information stored or transmitted in digital form that can be used in court as proof of a crime.

It is collected from:

  • Computers

  • Mobile phones

  • Servers

  • Cloud storage

  • CCTV systems

  • IoT devices

📘 2️⃣ Definition (Exam Ready)

Digital Evidence is electronic data that is stored, transmitted, or received in digital form and can be presented in a court of law to prove or disprove a fact in a cyber crime case.

📘 3️⃣ Characteristics of Digital Evidence

Digital evidence has special properties:

  1. Fragile – Can be easily altered or deleted

  2. Volatile – May disappear when power is turned off

  3. Duplicable – Exact copies can be made

  4. Hidden – May be encrypted or concealed

  5. Time-sensitive – Logs may be overwritten

📘 4️⃣ Types of Digital Evidence

🖥️ Computer-Based Evidence

  • Hard disk data

  • System logs

  • Installed programs

  • Deleted files

  • Browser history

📱 Mobile-Based Evidence

  • Call records

  • SMS/Chat messages

  • WhatsApp logs

  • GPS location

  • Photos and videos

🌐 Network-Based Evidence

  • IP address logs

  • Router logs

  • Firewall logs

  • Email headers

  • Server logs

☁️ Cloud-Based Evidence

  • Cloud storage files

  • Login history

  • Account activity logs

📘 5️⃣ Sources of Digital Evidence

  • RAM (volatile memory)

  • Hard drives

  • USB drives

  • Email servers

  • Social media platforms

  • CCTV DVR systems

📘 6️⃣ Volatile vs Non-Volatile Evidence

🔹 Volatile Evidence

  • Stored in RAM

  • Lost when system shuts down

  • Examples: running processes, active network connections

🔹 Non-Volatile Evidence

  • Stored permanently

  • Examples: hard disk data, USB data

📘 7️⃣ Handling Digital Evidence

Proper handling is critical because digital evidence is very sensitive.

Golden Rules:

  • Do not modify original device

  • Avoid turning off system without expert advice

  • Use write blockers

  • Maintain documentation

  • Follow legal procedures

📘 8️⃣ What is Chain of Custody?

Chain of Custody is the documented record that tracks the handling of digital evidence from collection to presentation in court.

It ensures:

  • Integrity

  • Authenticity

  • Accountability

📘 9️⃣ Why Chain of Custody is Important?

  • Prevents tampering

  • Maintains evidence credibility

  • Required in court

  • Protects investigators

If chain of custody is broken → Evidence may be rejected by court.

📘 🔟 Elements of Chain of Custody

Each record must include:

  1. Case number

  2. Description of evidence

  3. Date & time of collection

  4. Name of collector

  5. Location of collection

  6. Transfer details

  7. Storage location

  8. Signature of handlers

📘 1️⃣1️⃣ Steps in Maintaining Chain of Custody

Step 1: Identification

Label the evidence clearly.

Step 2: Documentation

Record:

  • Serial number

  • Device type

  • Condition

  • Date and time

Step 3: Collection

Use forensic tools and write blockers.

Step 4: Packaging

Seal in tamper-proof bags.

Step 5: Transportation

Transport securely with documentation.

Step 6: Storage

Store in secure evidence locker.

Step 7: Presentation

Produce original or forensic copy in court.

📘 1️⃣2️⃣ Forensic Imaging

Instead of examining original device:

  • Create exact bit-by-bit copy

  • Hash value is generated

  • Verify integrity using hash

📘 1️⃣3️⃣ What is Hash Value?

Hash is a unique digital fingerprint of data.

If data changes → hash changes.

Common hashing algorithms:

  • MD5

  • SHA-1

  • SHA-256

Used to verify integrity of evidence.

📘 1️⃣4️⃣ Legal Requirements in India

Digital evidence must comply with:

  • IT Act 2000

  • Indian Evidence Act (Section 65B)

  • Proper certification required

📘 1️⃣5️⃣ Challenges in Digital Evidence

  • Encryption

  • Cloud jurisdiction issues

  • Data deletion

  • Anti-forensic techniques

  • Large data volume

📘 1️⃣6️⃣ Best Practices

  • Always document everything

  • Never work on original device

  • Use certified forensic tools

  • Maintain evidence log

  • Follow legal authorization

📊 Investigation Flow Example

Seizure → Labeling → Forensic Imaging → Hash Calculation → Secure Storage → Analysis → Court Presentation

🎓 Short Exam Definitions

Digital Evidence: Electronic data used in court to prove cyber crime.

Chain of Custody: The documented process that records the handling of digital evidence to ensure its integrity and authenticity.

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