ZyXEL Communications P-660HW-D Series - Manual (Page 15)

P-660HW-D Series User’s Guide
Table of Contents 14
Chapter 9
Firewalls................................................................................................................ 142
9.1 Firewall Overview ............................................................................................142
9.2 Types of Firewalls ............................................................................................142
9.2.1 Packet Filtering Firewalls ........................................................................142
9.2.2 Application-level Firewalls ......................................................................143
9.2.3 Stateful Inspection Firewalls ..................................................................143
9.3 Introduction to ZyXEL’s Firewall .......................................................................143
9.3.1 Denial of Service Attacks ........................................................................144
9.4 Denial of Service ..............................................................................................144
9.4.1 Basics .....................................................................................................144
9.4.2 Types of DoS Attacks .............................................................................145
9.4.2.1 ICMP Vulnerability ........................................................................147
9.4.2.2 Illegal Commands (NetBIOS and SMTP) ......................................147
9.4.2.3 Traceroute .....................................................................................148
9.5 Stateful Inspection ............................................................................................148
9.5.1 Stateful Inspection Process ....................................................................149
9.5.2 Stateful Inspection and the ZyXEL device ..............................................149
9.5.3 TCP Security ...........................................................................................150
9.5.4 UDP/ICMP Security ................................................................................150
9.5.5 Upper Layer Protocols ............................................................................151
9.6 Guidelines for Enhancing Security with Your Firewall ......................................151
9.6.1 Security In General .................................................................................151
9.7 Packet Filtering Vs Firewall ..............................................................................152
9.7.1 Packet Filtering: ......................................................................................152
9.7.1.1 When To Use Filtering ...................................................................153
9.7.2 Firewall ...................................................................................................153
9.7.2.1 When To Use The Firewall ............................................................153
Chapter 10
Firewall Configuration ......................................................................................... 154
10.1 Access Methods .............................................................................................154
10.2 Firewall Policies Overview ............................................................................154
10.3 Rule Logic Overview .....................................................................................155
10.3.1 Rule Checklist .......................................................................................155
10.3.2 Security Ramifications ..........................................................................155
10.3.3 Key Fields For Configuring Rules .........................................................156
10.3.3.1 Action ..........................................................................................156
10.3.3.2 Service ........................................................................................156
10.3.3.3 Source Address ...........................................................................156
10.3.3.4 Destination Address ....................................................................156
10.4 Connection Direction ......................................................................................156
10.4.1 LAN to WAN Rules ...............................................................................157