ZyXEL Communications P-660H-TX V2 - VERSION 3-40 User Manual page 14

Table of Contents
Chapter 8
Firewalls................................................................................................................................. 111
8.1 Firewall Overview ..............................................................................................................111
8.2 Types of Firewalls ...............................................................................................................111
8.2.1 Packet Filtering Firewalls ..........................................................................................111
8.2.2 Application-level Firewalls .........................................................................................112
8.2.3 Stateful Inspection Firewalls ......................................................................................112
8.3 Introduction to ZyXEL's Firewall .........................................................................................112
8.3.1 Denial of Service Attacks ..........................................................................................113
8.4 Denial of Service ................................................................................................................113
8.4.1 Basics ........................................................................................................................113
8.4.2 Types of DoS Attacks ................................................................................................114
8.5 Stateful Inspection ..............................................................................................................116
8.5.1 Stateful Inspection Process .......................................................................................117
8.5.2 Stateful Inspection and the ZyXEL Device ................................................................118
8.5.3 TCP Security .............................................................................................................118
8.5.4 UDP/ICMP Security ...................................................................................................119
8.5.5 Upper Layer Protocols ..............................................................................................119
8.6 Guidelines for Enhancing Security with Your Firewall ....................................................... 120
8.6.1 Security In General .................................................................................................. 120
8.7 Packet Filtering Vs Firewall ............................................................................................... 121
8.7.1 Packet Filtering: ....................................................................................................... 121
8.7.2 Firewall ..................................................................................................................... 121
Chapter 9
Firewall Configuration .......................................................................................................... 123
9.1 Access Methods ................................................................................................................ 123
9.2 Firewall Policies Overview ................................................................................................. 123
9.3 Rule Logic Overview .......................................................................................................... 124
9.3.1 Rule Checklist .......................................................................................................... 124
9.3.2 Security Ramifications .............................................................................................. 124
9.3.3 Key Fields For Configuring Rules ........................................................................... 125
9.4 Connection Direction ......................................................................................................... 125
9.4.1 LAN to WAN Rules ................................................................................................... 126
9.4.2 Alerts ........................................................................................................................ 126
9.5 General Firewall Policy
9.6 Firewall Rules Summary ................................................................................................... 127
9.6.1 Configuring Firewall Rules ..................................................................................... 129
9.6.2 Customized Services .............................................................................................. 132
9.6.3 Configuring a Customized Service ......................................................................... 132
9.7 Example Firewall Rule ....................................................................................................... 133
9.8 Predefined Services .......................................................................................................... 137
9.9 Anti-Probing ....................................................................................................................... 139
14
................................................................................................... 126
P-660H-Tx v2 User's Guide