ZyXEL Communications 802.11g Wireless ADSL2+ 4-port VoIP IAD P-2602HWNLI - Manual (Page 17)

P-2602HWNLI User’s Guide
Table of Contents 17
13.3 Introduction to ZyXEL’s Firewall .....................................................................200
13.3.1 Denial of Service Attacks ......................................................................201
13.4 Denial of Service ............................................................................................201
13.4.1 Basics ...................................................................................................201
13.4.2 Types of DoS Attacks ...........................................................................202
13.4.2.1 ICMP Vulnerability ......................................................................204
13.4.2.2 Illegal Commands (NetBIOS and SMTP) ....................................204
13.4.2.3 Traceroute ...................................................................................205
13.5 Stateful Inspection ..........................................................................................205
13.5.1 Stateful Inspection Process ..................................................................206
13.5.2 Stateful Inspection on Your ZyXEL Device ...........................................207
13.5.3 TCP Security .........................................................................................207
13.5.4 UDP/ICMP Security ..............................................................................208
13.5.5 Upper Layer Protocols ..........................................................................208
13.6 Guidelines for Enhancing Security with Your Firewall ....................................209
13.6.1 Security In General ...............................................................................209
Chapter 14
Firewall Configuration ......................................................................................... 211
14.1 Access Methods .............................................................................................211
14.2 Firewall Policies Overview ............................................................................211
14.3 Rule Logic Overview .....................................................................................212
14.3.1 Rule Checklist .......................................................................................212
14.3.2 Security Ramifications ..........................................................................212
14.3.3 Key Fields For Configuring Rules .........................................................213
14.3.3.1 Action ..........................................................................................213
14.3.3.2 Service ........................................................................................213
14.3.3.3 Source Address ...........................................................................213
14.3.3.4 Destination Address ....................................................................213
14.4 Connection Direction ......................................................................................213
14.4.1 LAN to WAN Rules ...............................................................................214
14.4.2 Alerts .....................................................................................................214
14.5 Triangle Route ................................................................................................214
14.5.1 The “Triangle Route” Problem ..............................................................214
14.5.2 Solving the “Triangle Route” Problem ...................................................215
14.6 General Firewall Policy ...............................................................................216
14.7 Firewall Rules Summary ...............................................................................218
14.7.1 Configuring Firewall Rules ..................................................................219
14.7.2 Customized Services ...........................................................................222
14.7.3 Configuring A Customized Service .....................................................223
14.8 Example Firewall Rule ...................................................................................223
14.9 Predefined Services .......................................................................................227
14.10 Firewall Threshold ....................................................................................227