Layer 4 Attacks

Layer 4 Attacks - Transport Layer Exploitation

Layer 4 attacks target the Transport Layer protocols (TCP and UDP), exploiting connection management, flow control, and reliability mechanisms to compromise network communications, exhaust system resources, and bypass security controls.

Understanding Layer 4 Vulnerabilities

Connection State Exploitation: TCP’s stateful nature creates opportunities for session manipulation and resource exhaustion attacks.

Protocol Complexity: Transport layer features like sequence numbers, acknowledgments, and flow control provide attack vectors for sophisticated adversaries.

Resource Consumption: Both TCP and UDP can be leveraged to consume system resources through connection flooding and amplification attacks.

Transport Layer Attack Surface

TCP Vulnerabilities:

  • Sequence number prediction for session hijacking
  • Connection state manipulation
  • Resource exhaustion through connection flooding
  • Protocol-specific implementation weaknesses

UDP Vulnerabilities:

  • Connectionless nature enables amplification attacks
  • No built-in flow control or congestion management
  • Protocol-specific service exploitation
  • Reflection attack facilitation

Attack Categories Overview

Connection Manipulation

  • TCP Session Hijacking: Take control of established TCP connections
  • Sequence Number Prediction: Exploit predictable TCP sequence generation
  • Connection Reset Attacks: Forcibly terminate legitimate connections

Resource Exhaustion

  • SYN Flooding: Exhaust TCP connection tables through half-open connections
  • UDP Flooding: Overwhelm systems with high-volume UDP traffic
  • Amplification Attacks: Use protocol features to multiply attack traffic

Stealth and Evasion

  • Port Scanning Evasion: Advanced techniques to avoid detection during reconnaissance
  • Fragmentation Evasion: Split attacks across multiple packets
  • Timing Attacks: Exploit implementation differences through precise timing

Professional Context

Layer 4 attacks are essential for security professionals because they:

  • Test Connection Security: Validate session management and state handling
  • Assess Resource Limits: Identify system capacity under stress conditions
  • Evaluate Detection Systems: Test network monitoring and intrusion detection
  • Enable Advanced Exploitation: Provide positioning for application-layer attacks

Module Structure

This module covers five critical Layer 4 attack categories:

TCP Session Hijacking

Advanced techniques for predicting sequence numbers and taking control of established TCP connections.

UDP Flooding

Amplification attacks and resource exhaustion techniques using UDP protocol characteristics.

Port Scanning Evasion

Stealth scanning methods to avoid detection while gathering network intelligence.

Connection Exhaustion

Resource depletion attacks targeting connection tables and system capacity limits.

Protocol Vulnerabilities

Exploitation of protocol-specific weaknesses in TCP, UDP, and related transport mechanisms.

Layer 4 attacks bridge the gap between network infrastructure attacks and application-layer exploitation, providing critical skills for comprehensive security assessment.