Firewalls

3.

Types of Firewalls by Filtering Method

3.1.

Packet-Filtering Firewalls

3.1.1.

Operating Principles

3.1.1.1.

Stateless Inspection

3.1.1.2.

Individual Packet Analysis

3.1.1.3.

Header-Based Decisions

3.1.2.

Inspection Criteria

3.1.2.1.

Source IP Address

3.1.2.2.

Destination IP Address

3.1.2.3.

3.1.2.4.

Destination Port

3.1.2.5.

3.1.2.6.

3.1.3.

Implementation Methods

3.1.3.1.

Access Control Lists

3.1.3.2.

Routing Table Integration

3.1.4.

3.1.4.1.

High Performance

3.1.4.2.

Low Resource Usage

3.1.4.3.

3.1.5.

3.1.5.1.

No Connection Context

3.1.5.2.

Vulnerability to Spoofing

3.1.5.3.

Limited Application Awareness

3.2.

Circuit-Level Gateways

3.2.1.

Operating Principles

3.2.1.1.

Session Layer Monitoring

3.2.1.2.

Virtual Circuit Establishment

3.2.1.3.

Connection State Tracking

3.2.2.

TCP Handshake Monitoring

3.2.3.

Proxy Functionality

3.2.4.

3.2.4.1.

Network Address Hiding

3.2.4.2.

Low Processing Overhead

3.2.5.

3.2.5.1.

Limited Content Inspection

3.2.5.2.

Protocol-Specific Implementation

3.3.

Stateful Inspection Firewalls

3.3.1.

State Tracking Concepts

3.3.1.1.

Connection State Tables

3.3.1.2.

Session Information Storage

3.3.1.3.

Dynamic Rule Generation

3.3.2.

Connection Lifecycle Management

3.3.2.1.

Connection Establishment

3.3.2.2.

Data Transfer Monitoring

3.3.2.3.

Connection Termination

3.3.3.

State Table Management

3.3.3.1.

Memory Allocation

3.3.3.2.

Timeout Mechanisms

3.3.3.3.

Resource Optimization

3.3.4.

3.3.4.1.

Enhanced Security

3.3.4.2.

Context Awareness

3.3.4.3.

Dynamic Policy Adaptation

3.3.5.

3.3.5.1.

Resource Consumption

3.3.5.2.

3.3.5.3.

State Table Attacks

3.4.

Application-Level Gateways

3.4.1.

Proxy Architecture

3.4.1.1.

Client-Proxy Communication

3.4.1.2.

Proxy-Server Communication

3.4.1.3.

Connection Termination

3.4.2.

Deep Packet Inspection

3.4.2.1.

Application Layer Analysis

3.4.2.2.

Content Filtering

3.4.2.3.

Protocol Validation

3.4.3.

Protocol-Specific Proxies

3.4.3.1.

3.4.3.2.

3.4.3.3.

3.4.3.4.

3.4.4.

Content Analysis Capabilities

3.4.4.1.

Malware Detection

3.4.4.2.

Data Loss Prevention

3.4.4.3.

Content Modification

3.4.5.

3.4.5.1.

Granular Control

3.4.5.2.

Application Awareness

3.4.5.3.

Content Security

3.4.6.

3.4.6.1.

Performance Impact

3.4.6.2.

Protocol Limitations

3.4.6.3.

3.5.

Next-Generation Firewalls

3.5.1.

Integrated Security Features

3.5.1.1.

Traditional Firewall Functions

3.5.1.2.

Intrusion Prevention Systems

3.5.1.3.

Application Control

3.5.1.4.

User Identity Management

3.5.2.

Advanced Threat Protection

3.5.2.1.

Threat Intelligence Integration

3.5.2.2.

Behavioral Analysis

3.5.2.3.

3.5.3.

SSL/TLS Inspection

3.5.3.1.

Certificate Management

3.5.3.2.

Decryption Policies

3.5.3.3.

Performance Impact

3.5.4.

Application Awareness

3.5.4.1.

Application Identification

3.5.4.2.

Application Control Policies

3.5.4.3.

Bandwidth Management

3.5.5.

User Identity Integration

3.5.5.1.

Active Directory Integration

3.5.5.2.

LDAP Integration

3.5.5.3.

Single Sign-On Support

3.5.6.

3.5.6.1.

Comprehensive Security

3.5.6.2.

Centralized Management

3.5.6.3.

Advanced Threat Detection

3.5.7.

3.5.7.1.

Cost and Complexity

3.5.7.2.

Performance Overhead

3.5.7.3.

Management Complexity

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4. Types of Firewalls by Deployment Model