P-660H/HW-T Series User’ Guide
Chapter 10 Firewalls
122
Figure 48
Three-Way Handshake
Under normal circumstances, the application that initiates a session sends a SYN
(synchronize) packet to the receiving server. The receiver sends back an ACK
(acknowledgment) packet and its own SYN, and then the initiator responds with an ACK
(acknowledgment). After this handshake, a connection is established.
•
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 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 49
SYN Flood
• 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.
7
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
Summary of Contents for P-660H Series
Page 2: ......
Page 10: ...P 660H HW T Series User Guide 9 Customer Support ...
Page 32: ...P 660H HW T Series User Guide 31 List of Figures ...
Page 38: ...P 660H HW T Series User Guide 37 List of Tables ...
Page 42: ...P 660H HW T Series User Guide 41 Introduction to DSL ...
Page 62: ...P 660H HW T Series User Guide 61 Chapter 3 Wizard Setup for Internet Access ...
Page 90: ...P 660H HW T Series User Guide 89 Chapter 5 Wireless LAN ...
Page 132: ...P 660H HW T Series User Guide 131 Chapter 10 Firewalls ...
Page 162: ...P 660H HW T Series User Guide 161 Chapter 13 Remote Management Configuration ...
Page 176: ...P 660H HW T Series User Guide 175 Chapter 14 Universal Plug and Play UPnP ...
Page 182: ...P 660H HW T Series User Guide 181 Chapter 15 Logs Screens ...
Page 196: ...P 660H HW T Series User Guide 195 Chapter 16 Media Bandwidth Management Advanced Setup ...
Page 208: ...P 660H HW T Series User Guide 207 Chapter 17 Maintenance ...
Page 218: ...P 660H HW T Series User Guide 217 Chapter 19 Menu 1 General Setup ...
Page 222: ...P 660H HW T Series User Guide 221 Chapter 20 Menu 2 WAN Backup Setup ...
Page 226: ...P 660H HW T Series User Guide 225 Chapter 21 Menu 3 LAN Setup ...
Page 230: ...P 660H HW T Series User Guide 229 Chapter 22 Wireless LAN Setup ...
Page 236: ...P 660H HW T Series User Guide 235 Chapter 23 Internet Access ...
Page 250: ...P 660H HW T Series User Guide 249 Chapter 25 Static Route Setup ...
Page 254: ...P 660H HW T Series User Guide 253 Chapter 26 Bridging Setup ...
Page 270: ...P 660H HW T Series User Guide 269 Chapter 27 Network Address Translation NAT ...
Page 286: ...P 660H HW T Series User Guide 285 Chapter 29 Filter Configuration ...
Page 306: ...P 660H HW T Series User Guide 305 Chapter 32 System Information and Diagnosis ...
Page 318: ...P 660H HW T Series User Guide 317 Chapter 33 Firmware and Configuration File Maintenance ...
Page 324: ...P 660H HW T Series User Guide 323 Chapter 34 System Maintenance ...
Page 328: ...P 660H HW T Series User Guide 327 Chapter 35 Remote Management ...
Page 338: ...P 660H HW T Series User Guide 337 Chapter 36 IP Policy Routing ...
Page 342: ...P 660H HW T Series User Guide 341 Chapter 37 Call Scheduling ...
Page 358: ...P 660H HW T Series User Guide 357 Appendix A ...
Page 360: ...P 660H HW T Series User Guide 359 Appendix B ...
Page 384: ...P 660H HW T Series User Guide 383 Appendix D ...
Page 388: ...P 660H HW T Series User Guide 387 Appendix F ...
Page 394: ...P 660H HW T Series User Guide 393 Appendix G ...
Page 398: ...P 660H HW T Series User Guide 397 Appendix H ...
Page 401: ...P 660H HW T Series User Guide Appendix I 400 ...
Page 402: ...P 660H HW T Series User Guide 401 Appendix I ...
Page 456: ...P 660H HW T Series User Guide 455 Appendix M ...