ZyXEL Communications ZyWall 35 User Manual page 13

9.4.2.1 ICMP Vulnerability ........................................................................170
9.4.2.2 Illegal Commands (NetBIOS and SMTP) ......................................170
9.4.2.3 Traceroute .....................................................................................171
9.5 Stateful Inspection ............................................................................................171
9.5.1 Stateful Inspection Process ....................................................................172
9.5.2 Stateful Inspection and the ZyWALL .......................................................173
9.5.3 TCP Security ...........................................................................................173
9.5.4 UDP/ICMP Security ................................................................................174
9.5.5 Upper Layer Protocols ............................................................................174
9.6 Guidelines For Enhancing Security With Your Firewall ....................................175
9.7 Packet Filtering Vs Firewall ..............................................................................175
9.7.1 Packet Filtering: ......................................................................................175
9.7.1.1 When To Use Filtering ...................................................................175
9.7.2 Firewall ...................................................................................................176
9.7.2.1 When To Use The Firewall ............................................................176
Chapter 10
Firewall Screens................................................................................................... 177
10.1 Access Methods .............................................................................................177
10.2 Firewall Policies Overview .............................................................................177
10.3 Rule Logic Overview ......................................................................................178
10.3.1 Rule Checklist .......................................................................................178
10.3.2 Security Ramifications ..........................................................................179
10.3.3 Key Fields For Configuring Rules .........................................................179
10.3.3.1 Action ..........................................................................................179
10.3.3.2 Service ........................................................................................179
10.3.3.3 Source Address ...........................................................................179
10.3.3.4 Destination Address ....................................................................179
10.4 Connection Direction Examples .....................................................................179
10.4.1 LAN To WAN Rules ..............................................................................180
10.4.2 WAN To LAN Rules ..............................................................................180
10.5 Alerts ..............................................................................................................181
10.6 Configuring Firewall .......................................................................................181
10.6.1 Rule Summary ......................................................................................184
10.6.2 Configuring Firewall Rules ....................................................................185
10.6.3 Configuring Custom Services ...............................................................188
10.7 Example Firewall Rule ...................................................................................188
10.8 Predefined Services .......................................................................................192
10.9 Anti-Probing ...................................................................................................194
10.10 DoS Thresholds ...........................................................................................195
10.10.1 Threshold Values ................................................................................196
10.10.2 Half-Open Sessions ............................................................................196
10.10.2.1 TCP Maximum Incomplete and Blocking Time .........................196
ZyWALL 35 User's Guide
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