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                                          20.1 | 
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                                          Introduction
                                                 
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                                          20.1.1 | 
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                                          History and Background
                                                   
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                                          20.1.1.1 | 
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                                          Changing Network Models
                                                     
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                                          20.1.2 | 
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                                          Progression of Network Security Mechanisms
                                                   
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                                          20.1.2.1 | 
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                                          Router Access Control Lists
                                                     
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                                          20.1.2.2 | 
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                                          Dedicated Host-based Firewall Applications
                                                     
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                                          20.1.2.3 | 
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                                          Purpose-built Firewall Appliances
                                                     
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                                          20.1.2.4 | 
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                                          Personal Firewalls
                                                     
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                                          20.2 | 
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                                          Role of Network Security Mechanisms
                                                 
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                                          20.2.1 | 
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                                          Perimeter Protection
                                                   
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                                          20.2.1.1 | 
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                                          Control of Allowed Paths
                                                     
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                                          20.2.1.2 | 
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                                          Intrusion Detection
                                                     
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                                          20.2.2 | 
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                                          Additional Roles of the Firewall and Proxy Server
                                                   
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                                          20.2.2.1 | 
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                                          Intrusion Response
                                                     
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                                          20.2.2.2 | 
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                                          Encryption
                                                     
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                                          20.2.2.3 | 
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                                          Content Inspection
                                                     
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                                          20.2.2.4 | 
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                                          Caching
                                                     
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                                          20.3 | 
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                                          Technical Detail: Firewalls
                                                 
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                                          20.3.1 | 
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                                          Security Tasks
                                                   
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                                          20.3.1.1 | 
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                                          Authorization
                                                     
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                                          20.3.1.2 | 
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                                          Availability
                                                     
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                                          20.3.1.3 | 
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                                          Accounting and Audit
                                                     
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                                          20.3.2 | 
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                                          Firewall Architectures
                                                   
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                                          20.3.2.1 | 
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                                          Rule Processing on Routing Devices
                                                     
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                                          20.3.2.2 | 
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                                          Packet-filtering Firewalls
                                                     
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                                          20.3.2.3 | 
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                                          Stateful Inspection Firewalls
                                                     
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                                          20.3.2.4 | 
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                                          Application Gateway Firewalls
                                                     
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                                          20.3.2.5 | 
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                                          Hybrid Firewalls
                                                     
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                                          20.3.3 | 
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                                          Technical Detail: Proxy Servers
                                                   
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                                          20.4 | 
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                                          Available and Emerging Technologies
                                                 
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                                          20.4.1 | 
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                                          Consolidated Management Consoles
                                                   
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                                          20.4.2 | 
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                                          Unified Intrusion Detection
                                                   
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                                          20.4.3 | 
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                                          Unified Alerting and Reporting
                                                   
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                                          20.4.4 | 
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                                          Content Vectoring
                                                   
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                                          20.4.5 | 
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                                          Multifunction Devices
                                                   
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                                          20.4.6 | 
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                                          Automated Allowed-Path Inspection
                                                   
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                                          20.5 | 
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                                          Successful Deployment of Network Security Mechanisms
                                                 
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                                          20.5.1 | 
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                                          Screened Subnet Firewall Architectures
                                                   
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                                          20.5.2 | 
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                                          Management and Monitoring Strategies
                                                   
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                                          20.5.2.1 | 
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                                          Direct Console Method
                                                     
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                                          20.5.2.2 | 
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                                          Out-of-Band Method
                                                     
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                                          20.5.2.3 | 
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                                          Isolated In-Band Management
                                                     
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                                          20.5.2.4 | 
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                                          Full In-Band Managemen
                                                     
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                                          20.5.3 | 
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                                          Firewall and Proxy Server Configuration and Management
                                                   
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                                          20.5.3.1 | 
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                                          Rule Creation
                                                     
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                                          20.5.3.2 | 
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                                          Implicit Rules and Default Configurations
                                                     
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                                          20.5.4 | 
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                                          A Constantly Changing Security Landscape
                                                   
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                                          20.5.4.1 | 
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                                          Full Disclosure Security Forums and Resources
                                                     
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                                          20.5.4.2 | 
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                                          Vendor Security Alerts and Updates
                                                     
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                                          20.5.4.3 | 
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                                          Internal Technical Resources
                                                     
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                                          20.6 | 
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                                          For Further Reading
                                                 
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