ZyXEL Communications P-660H Series User Manual page 15

Chapter 9
Firewalls................................................................................................................ 144
9.1 Firewall Overview ............................................................................................144
9.2 Types of Firewalls ............................................................................................144
9.3 Introduction to ZyXEL's Firewall .......................................................................145
9.4 Denial of Service ..............................................................................................146
9.5 Stateful Inspection ............................................................................................150
9.6 Guidelines for Enhancing Security with Your Firewall ......................................153
9.7 Packet Filtering Vs Firewall ..............................................................................154
Chapter 10
Firewall Configuration ......................................................................................... 156
10.1 Access Methods .............................................................................................156
10.2 Firewall Policies Overview ............................................................................156
10.3 Rule Logic Overview .....................................................................................157
10.4 Connection Direction ......................................................................................158
Table of Contents
9.2.1 Packet Filtering Firewalls ........................................................................144
9.2.2 Application-level Firewalls ......................................................................145
9.2.3 Stateful Inspection Firewalls ..................................................................145
9.3.1 Denial of Service Attacks ........................................................................146
9.4.1 Basics .....................................................................................................146
9.4.2 Types of DoS Attacks .............................................................................147
9.4.2.1 ICMP Vulnerability ........................................................................149
9.4.2.2 Illegal Commands (NetBIOS and SMTP) ......................................149
9.4.2.3 Traceroute .....................................................................................150
9.5.1 Stateful Inspection Process ....................................................................151
9.5.2 Stateful Inspection and the ZyXEL Device ..............................................151
9.5.3 TCP Security ...........................................................................................152
9.5.4 UDP/ICMP Security ................................................................................152
9.5.5 Upper Layer Protocols ............................................................................153
9.6.1 Security In General .................................................................................153
9.7.1 Packet Filtering: ......................................................................................154
9.7.1.1 When To Use Filtering ...................................................................155
9.7.2 Firewall ...................................................................................................155
9.7.2.1 When To Use The Firewall ............................................................155
10.3.1 Rule Checklist .......................................................................................157
10.3.2 Security Ramifications ..........................................................................157
10.3.3 Key Fields For Configuring Rules .........................................................158
10.3.3.1 Action ..........................................................................................158
10.3.3.2 Service ........................................................................................158
10.3.3.3 Source Address ...........................................................................158
10.3.3.4 Destination Address ....................................................................158
10.4.1 LAN to WAN Rules ...............................................................................159
P-660H/HW-D Series User's Guide
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