ZyXEL Communications ADSL VoIP IAD with 802.11g Wireless 2602HW Series - Manual (Page 14)

Prestige 2602HW Series User’s Guide
14 Table of Contents
Chapter 13
Firewalls................................................................................................................ 155
13.1 Firewall Overview ...........................................................................................155
13.2 Types of Firewalls ..........................................................................................155
13.2.1 Packet Filtering Firewalls ......................................................................155
13.2.2 Application-level Firewalls ....................................................................155
13.2.3 Stateful Inspection Firewalls ................................................................156
13.3 Introduction to ZyXEL’s Firewall .....................................................................156
13.3.1 Denial of Service Attacks ......................................................................157
13.4 Denial of Service ............................................................................................157
13.4.1 Basics ...................................................................................................157
13.4.2 Types of DoS Attacks ...........................................................................158
13.4.2.1 ICMP Vulnerability ......................................................................160
13.4.2.2 Illegal Commands (NetBIOS and SMTP) ....................................160
13.4.2.3 Traceroute ...................................................................................161
13.5 Stateful Inspection ..........................................................................................161
13.5.1 Stateful Inspection Process ..................................................................162
13.5.2 Stateful Inspection and the Prestige .....................................................163
13.5.3 TCP Security .........................................................................................163
13.5.4 UDP/ICMP Security ..............................................................................164
13.5.5 Upper Layer Protocols ..........................................................................164
13.6 Guidelines for Enhancing Security with Your Firewall ....................................164
13.6.1 Security In General ...............................................................................165
13.7 Packet Filtering Vs Firewall ............................................................................166
13.7.1 Packet Filtering: ....................................................................................166
13.7.1.1 When To Use Filtering .................................................................166
13.7.2 Firewall .................................................................................................166
13.7.2.1 When To Use The Firewall ..........................................................166
Chapter 14
Firewall Configuration ......................................................................................... 169
14.1 Access Methods .............................................................................................169
14.2 Firewall Policies Overview .............................................................................169
14.3 Rule Logic Overview ......................................................................................170
14.3.1 Rule Checklist .......................................................................................170
14.3.2 Security Ramifications ..........................................................................170
14.3.3 Key Fields For Configuring Rules .........................................................171
14.3.3.1 Action ..........................................................................................171
14.3.3.2 Service ........................................................................................171
14.3.3.3 Source Address ...........................................................................171
14.3.3.4 Destination Address ....................................................................171
14.4 Connection Direction Example .......................................................................171
14.4.1 LAN to WAN Rules ...............................................................................172