Chapter 16 Firewall
VSG1435-B101 Series User’s Guide
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16.1.2 What You Need to Know
SYN Attack
A SYN attack floods a targeted system with a series of SYN packets. Each packet
causes the targeted system to issue a SYN-ACK response. While the targeted
system waits for the ACK that follows the SYN-ACK, it queues up all outstanding
SYN-ACK responses on a backlog queue. SYN-ACKs are moved off the queue only
when an ACK comes back or when an internal timer 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.
DoS
Denials of Service (DoS) attacks are aimed at devices and networks with a
connection to the Internet. Their goal is not to steal information, but to disable a
device or network so users no longer have access to network resources. The
ZyXEL Device is pre-configured to automatically detect and thwart all known DoS
attacks.
DDoS
A DDoS attack is one in which multiple compromised systems attack a single
target, thereby causing denial of service for users of the targeted system.
LAND Attack
In a LAND attack, hackers flood SYN packets into the network with a spoofed
source IP address of the target 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.
Ping of Death
Ping of Death uses a "ping" utility to create and send an IP packet that exceeds
the maximum 65,536 bytes of data allowed by the IP specification. This may
cause systems to crash, hang or reboot.
SPI
Stateful Packet Inspection (SPI) tracks each connection crossing the firewall and
makes sure it is valid. Filtering decisions are based not only on rules but also
context. For example, traffic from the WAN may only be allowed to cross the
firewall in response to a request from the LAN.
Summary of Contents for VSG1435-B101 - V1.10
Page 2: ......
Page 8: ...Safety Warnings VSG1435 B101 Series User s Guide 8 ...
Page 10: ...Contents Overview VSG1435 B101 Series User s Guide 10 ...
Page 20: ...Table of Contents VSG1435 B101 Series User s Guide 20 ...
Page 21: ...21 PART I User s Guide ...
Page 22: ...22 ...
Page 42: ...Chapter 2 The Web Configurator VSG1435 B101 Series User s Guide 42 ...
Page 71: ...71 PART II Technical Reference ...
Page 72: ...72 ...
Page 78: ...Chapter 5 Network Map and Status Screens VSG1435 B101 Series User s Guide 78 ...
Page 150: ...Chapter 8 Home Networking VSG1435 B101 Series User s Guide 150 ...
Page 154: ...Chapter 9 Static Routing VSG1435 B101 Series User s Guide 154 ...
Page 178: ...Chapter 11 Policy Forwarding VSG1435 B101 Series User s Guide 178 ...
Page 196: ...Chapter 12 Network Address Translation NAT VSG1435 B101 Series User s Guide 196 ...
Page 202: ...Chapter 13 Dynamic DNS Setup VSG1435 B101 Series User s Guide 202 ...
Page 228: ...Chapter 16 Firewall VSG1435 B101 Series User s Guide 228 ...
Page 234: ...Chapter 18 Parental Control VSG1435 B101 Series User s Guide 234 ...
Page 282: ...Chapter 25 Traffic Status VSG1435 B101 Series User s Guide 282 ...
Page 286: ...Chapter 26 IGMP Status VSG1435 B101 Series User s Guide 286 ...
Page 294: ...Chapter 28 Remote Management VSG1435 B101 Series User s Guide 294 ...
Page 298: ...Chapter 29 Time Settings VSG1435 B101 Series User s Guide 298 ...
Page 302: ...Chapter 30 Logs Setting VSG1435 B101 Series User s Guide 302 ...
Page 318: ...Chapter 34 Troubleshooting VSG1435 B101 Series User s Guide 318 ...
Page 348: ...Appendix A Setting up Your Computer s IP Address VSG1435 B101 Series User s Guide 348 ...
Page 358: ...Appendix B IP Addresses and Subnetting VSG1435 B101 Series User s Guide 358 ...
Page 384: ...Appendix D Wireless LANs VSG1435 B101 Series User s Guide 384 ...