ZyXEL Communications P-660HW-T - V2, User Manual

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P-660HW-T v2 User’s Guide
Table of Contents 15
9.4 Denial of Service ..............................................................................................139
9.4.1 Basics .....................................................................................................139
9.4.2 Types of DoS Attacks .............................................................................140
9.4.2.1 ICMP Vulnerability ........................................................................142
9.4.2.2 Illegal Commands (NetBIOS and SMTP) ......................................142
9.4.2.3 Traceroute .....................................................................................143
9.5 Stateful Inspection ............................................................................................143
9.5.1 Stateful Inspection Process ....................................................................144
9.5.2 Stateful Inspection and the ZyXEL Device ..............................................144
9.5.3 TCP Security ...........................................................................................145
9.5.4 UDP/ICMP Security ................................................................................145
9.5.5 Upper Layer Protocols ............................................................................146
9.6 Guidelines for Enhancing Security with Your Firewall ......................................146
9.6.1 Security In General .................................................................................146
9.7 Packet Filtering Vs Firewall ..............................................................................147
9.7.1 Packet Filtering: ......................................................................................147
9.7.1.1 When To Use Filtering ...................................................................148
9.7.2 Firewall ...................................................................................................148
9.7.2.1 When To Use The Firewall ............................................................148
Chapter 10
Firewall Configuration ......................................................................................... 149
10.1 Access Methods .............................................................................................149
10.2 Firewall Policies Overview ............................................................................149
10.3 Rule Logic Overview .....................................................................................150
10.3.1 Rule Checklist .......................................................................................150
10.3.2 Security Ramifications ..........................................................................150
10.3.3 Key Fields For Configuring Rules ........................................................151
10.3.3.1 Action ..........................................................................................151
10.3.3.2 Service ........................................................................................151
10.3.3.3 Source Address ...........................................................................151
10.3.3.4 Destination Address ....................................................................151
10.4 Connection Direction ......................................................................................151
10.4.1 LAN to WAN Rules ...............................................................................152
10.4.2 Alerts .....................................................................................................152
10.5 General Firewall Policy ...............................................................................152
10.6 Firewall Rules Summary ...............................................................................153
10.6.1 Configuring Firewall Rules ..................................................................155
10.6.2 Customized Services ...........................................................................158
10.6.3 Configuring a Customized Service .....................................................159
10.7 Example Firewall Rule ...................................................................................159
10.8 Predefined Services .......................................................................................163
10.9 Anti-Probing ..................................................................................................165