Cyber Security Network Transport

🚚 Cyber Security Network Transport (Layer 4) In-Depth

👉 Most real-world hacking, scanning, and DDoS attacks target this layer.

 What is the Transport Layer?

The Transport Layer is responsible for:

• End-to-end communication

• Data segmentation & reassembly

• Port numbers

• Flow control

• Error control

📌 In simple words:

Transport Layer decides how data is delivered safely and in order

 Key Responsibilities (Security View)

1️⃣ Port Addressing

Ports identify applications/services.

📌 Hackers use port scanning to find vulnerable services.

2️⃣ Segmentation & Reassembly

• Large data → split into segments

• Segments sent separately

• Reassembled at destination

⚠️ Attackers exploit segmentation to confuse firewalls.

3️⃣ Flow Control

Prevents sender from overwhelming receiver.

🛡 Prevents system crash & buffer overflow

4️⃣ Error Control

Ensures data arrives correctly using:

• Acknowledgements (ACK)

• Retransmission

 Transport Layer Protocols

🔵 TCP (Transmission Control Protocol)

• Connection-oriented

• Reliable

• Slower but secure

✔ Used for: Web, Email, File transfer

🟠 UDP (User Datagram Protocol)

• Connectionless

• Faster

• No guarantee of delivery

✔ Used for: Video calls, DNS, gaming

 TCP vs UDP (Cyber Security View)

 TCP Three-Way Handshake (Very Important)

1️⃣ SYN
2️⃣ SYN-ACK
3️⃣ ACK

📌 This process creates a session

⚠️ Attackers exploit this using SYN Flood attacks

🔴 Transport Layer Attacks (In-Depth)

1️⃣ Port Scanning

Finding open ports to identify services.

🛠 Example:

• TCP Scan

• UDP Scan

📌 First step of hacking

2️⃣ SYN Flood Attack

Attacker sends many SYN requests but never completes handshake.

🎯 Result:

• Server resources exhausted

• Legit users blocked

🛡 Defense:

• SYN cookies

• Rate limiting

• Firewalls

3️⃣ UDP Flood Attack

Sending massive UDP packets.

🎯 Result:

• Bandwidth exhaustion

🛡 Defense:

• Traffic filtering

• IDS/IPS

4️⃣ Session Hijacking

Taking over an active TCP session.

🎯 Used to:

• Steal login sessions

• Bypass authentication

🛡 Defense:

• Encryption (TLS)

• Secure session handling

5️⃣ Replay Attacks

Captured packets resent to gain access.

🛡 Defense:

• Timestamps

• Nonces

• Encryption

 Transport Layer Firewalls

Filters traffic based on:

• Port number

• Protocol (TCP/UDP)

• Connection state

📌 Faster than application firewalls but less intelligent

Transport Layer vs Network Layer (Quick View)

📌 Hackers move Layer 3 → Layer 4

Important Commands (Layer 4 Focus)

🎯 Why Transport Layer is CRITICAL in Cyber Security

✔ Controls applications
✔ Main target of DDoS
✔ Basis of scanning & exploitation
✔ Determines service exposure

📌 Open port = open risk