Chapter 15 Firewall
VMG1312-B Series User’s Guide
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15.1.2 What You Need to Know
SYN Attack
A SYN at t ack floods a t arget ed syst em wit h a series of SYN packet s. Each packet causes t he
t arget ed syst em t o issue a SYN- ACK response. While t he t arget ed syst em wait s for t he ACK t hat
follows t he SYN- ACK, it queues up all out st anding SYN- ACK responses on a backlog queue. SYN-
ACKs are m oved off t he queue only w hen an ACK com es back or when an int ernal t im er t erm inat es
t he t hree- way handshake. Once t he queue is full, t he syst em will ignore all incom ing SYN request s,
m aking t he syst em unavailable for legit im at e users.
DoS
Denials of Service ( DoS) at t acks are aim ed at devices and net works wit h a connect ion t o t he
I nt ernet . Their goal is not t o st eal inform at ion, but t o disable a device or net work so users no longer
have access t o net work resources. The ZyXEL Device is pre- configured t o aut om at ically det ect and
t hwart all known DoS at t acks.
DDoS
A DDoS at t ack is one in which m ult iple com prom ised syst em s at t ack a single t arget , t hereby
causing denial of service for users of t he t arget ed syst em .
LAND Attack
I n a LAND at t ack, hackers flood SYN packet s int o t he net work wit h a spoofed source I P address of
t he t arget syst em . This m akes it appear as if t he host com put er sent t he packet s t o it self, m aking
t he syst em unavailable while t he t arget syst em t ries t o respond t o it self.
Ping of Death
Ping of Deat h uses a " ping" ut ilit y t o creat e and send an I P packet t hat exceeds t he m axim um
65,536 byt es of dat a allowed by t he I P specificat ion. This m ay cause syst em s t o crash, hang or
reboot .
SPI
St at eful Packet I nspect ion ( SPI ) t racks each connect ion crossing t he firewall and m akes sure it is
valid. Filt ering decisions are based not only on rules but also cont ext . For exam ple, t raffic from t he
WAN m ay only be allowed t o cross t he firewall in response t o a request from t he LAN.
Summary of Contents for VMG1312-B Series
Page 4: ...Contents Overview VMG1312 B Series User s Guide 4 Troubleshooting 289 ...
Page 14: ...Table of Contents VMG1312 B Series User s Guide 14 ...
Page 15: ...15 PART I User s Guide ...
Page 16: ...16 ...
Page 30: ...Chapter 2 The Web Configurator VMG1312 B Series User s Guide 30 ...
Page 35: ...Chapter 4 Tutorials VMG1312 B Series User s Guide 35 7 Click Apply to save your settings ...
Page 77: ...77 PART II Technical Reference ...
Page 78: ...78 ...
Page 166: ...Chapter 9 Routing VMG1312 B Series User s Guide 166 ...
Page 184: ...Chapter 10 Quality of Service QoS VMG1312 B Series User s Guide 184 ...
Page 210: ...Chapter 13 Interface Group VMG1312 B Series User s Guide 210 ...
Page 226: ...Chapter 15 Firewall VMG1312 B Series User s Guide 226 ...
Page 232: ...Chapter 17 Parental Control VMG1312 B Series User s Guide 232 ...
Page 242: ...Chapter 19 Certificates VMG1312 B Series User s Guide 242 ...
Page 246: ...Chapter 20 Log VMG1312 B Series User s Guide 246 ...
Page 250: ...Chapter 21 Traffic Status VMG1312 B Series User s Guide 250 ...
Page 256: ...Chapter 24 IGMP Status VMG1312 B Series User s Guide 256 ...
Page 260: ...Chapter 25 xDSL Statistics VMG1312 B Series User s Guide 260 ...
Page 262: ...Chapter 26 User Account VMG1312 B Series User s Guide 262 ...
Page 268: ...Chapter 29 TR 064 VMG1312 B Series User s Guide 268 ...
Page 272: ...Chapter 30 Time Settings VMG1312 B Series User s Guide 272 ...
Page 278: ...Chapter 32 Logs Setting VMG1312 B Series User s Guide 278 ...
Page 296: ...Chapter 36 Troubleshooting VMG1312 B Series User s Guide 296 ...
Page 336: ...Appendix C Pop up Windows JavaScripts and Java Permissions VMG1312 B Series User s Guide 336 ...
Page 350: ...Appendix D Wireless LANs VMG1312 B Series User s Guide 350 ...
Page 374: ...VMG1312 B Series User s Guide 374 Index ...