ZyWALL 70 User’s Guide
Chapter 9 Firewalls
171
response. While the targeted system waits for the ACK that follows
the SYN-ACK, it queues up all outstanding SYN-ACK responses on
what is known as a backlog queue. SYN-ACKs are moved off the
queue only when an ACK comes back or when an internal timer
(which is set at relatively long intervals) terminates the three-way
handshake. Once the queue is full, the system will ignore all
incoming SYN requests, making the system unavailable for
legitimate users.
Figure 63
SYN Flood
b
In a
LAND Attack
, hackers flood SYN packets into the network with
a spoofed source IP address of the targeted system. This makes it
appear as if the host computer sent the packets to itself, making the
system unavailable while the target system tries to respond to itself.
• A
brute-force
attack, such as a "Smurf" attack, targets a feature in the IP specification
known as directed or subnet broadcasting, to quickly flood the target network with
useless data. A Smurf hacker floods a router with Internet Control Message Protocol
(ICMP) echo request packets (pings). Since the destination IP address of each packet is
the broadcast address of the network, the router will broadcast the ICMP echo request
packet to all hosts on the network. If there are numerous hosts, this will create a large
amount of ICMP echo request and response traffic. If a hacker chooses to spoof the
source IP address of the ICMP echo request packet, the resulting ICMP traffic will not
only clog up the "intermediary" network, but will also congest the network of the spoofed
source IP address, known as the "victim" network. This flood of broadcast traffic
consumes all available bandwidth, making communications impossible.
Summary of Contents for ZyWALL 70
Page 1: ...ZyWALL 70 Internet Security Appliance User s Guide Version 3 64 3 2005 ...
Page 2: ......
Page 38: ...ZyWALL 70 User s Guide 38 List of Figures ...
Page 46: ...ZyWALL 70 User s Guide 46 List of Tables ...
Page 74: ...ZyWALL 70 User s Guide 74 Chapter 2 Introducing the Web Configurator ...
Page 92: ...ZyWALL 70 User s Guide 92 Chapter 3 Wizard Setup ...
Page 102: ...ZyWALL 70 User s Guide 102 Chapter 4 LAN Screens ...
Page 108: ...ZyWALL 70 User s Guide 108 Chapter 5 Bridge Screens ...
Page 130: ...ZyWALL 70 User s Guide 130 Chapter 6 Wireless LAN ...
Page 136: ...ZyWALL 70 User s Guide 136 Chapter 7 WAN Screens Figure 45 WAN General ...
Page 155: ...ZyWALL 70 User s Guide Chapter 7 WAN Screens 155 Figure 55 Dial Backup Setup ...
Page 234: ...ZyWALL 70 User s Guide 234 Chapter 13 Introduction to IPSec ...
Page 275: ...ZyWALL 70 User s Guide Chapter 15 Certificates 275 Figure 125 My Certificate Details ...
Page 294: ...ZyWALL 70 User s Guide 294 Chapter 16 Authentication Server Figure 136 Local User Database ...
Page 314: ...ZyWALL 70 User s Guide 314 Chapter 17 Network Address Translation NAT ...
Page 318: ...ZyWALL 70 User s Guide 318 Chapter 18 Static Route ...
Page 324: ...ZyWALL 70 User s Guide 324 Chapter 19 Policy Route ...
Page 340: ...ZyWALL 70 User s Guide 340 Chapter 20 Bandwidth Management ...
Page 376: ...ZyWALL 70 User s Guide 376 Chapter 22 Remote Management ...
Page 390: ...ZyWALL 70 User s Guide 390 Chapter 24 Logs Screens Figure 194 Log Settings ...
Page 413: ...ZyWALL 70 User s Guide Chapter 25 Maintenance 413 Figure 216 Restart Screen ...
Page 414: ...ZyWALL 70 User s Guide 414 Chapter 25 Maintenance ...
Page 440: ...ZyWALL 70 User s Guide 440 Chapter 28 WAN and Dial Backup Setup ...
Page 456: ...ZyWALL 70 User s Guide 456 Chapter 31 DMZ Setup ...
Page 460: ...ZyWALL 70 User s Guide 460 Chapter 32 Route Setup ...
Page 470: ...ZyWALL 70 User s Guide 470 Chapter 33 Remote Node Setup ...
Page 522: ...ZyWALL 70 User s Guide 522 Chapter 39 System Information Diagnosis ...
Page 538: ...ZyWALL 70 User s Guide 538 Chapter 40 Firmware and Configuration File Maintenance ...
Page 550: ...ZyWALL 70 User s Guide 550 Chapter 42 Remote Management ...
Page 558: ...ZyWALL 70 User s Guide 558 Chapter 43 IP Policy Routing ...
Page 573: ...ZyWALL 70 User s Guide Chapter 45 Troubleshooting 573 Figure 360 Java Sun ...
Page 574: ...ZyWALL 70 User s Guide 574 Chapter 45 Troubleshooting ...
Page 582: ...ZyWALL 70 User s Guide 582 Appendix B Removing and Installing a Fuse ...
Page 602: ...ZyWALL 70 User s Guide 602 Appendix D IP Subnetting ...
Page 608: ...ZyWALL 70 User s Guide 608 Appendix F PPTP ...
Page 626: ...ZyWALL 70 User s Guide 626 Appendix H Triangle Route ...
Page 656: ...ZyWALL 70 User s Guide 656 Appendix K Importing Certificates ...
Page 658: ...ZyWALL 70 User s Guide 658 Appendix L Command Interpreter ...
Page 664: ...ZyWALL 70 User s Guide 664 Appendix M Firewall Commands ...
Page 668: ...ZyWALL 70 User s Guide 668 Appendix N NetBIOS Filter Commands ...
Page 674: ...ZyWALL 70 User s Guide 674 Appendix P Brute Force Password Guessing Protection ...
Page 696: ...ZyWALL 70 User s Guide 696 Appendix R Log Descriptions ...