ZyXEL 793H Guía Del Usuario
Chapter 8 Firewalls
P-793H User’s Guide
119
8.3.1 Denial of Service Attacks
Figure 52 ZyXEL Device Firewall Application
8.4 Denial of Service
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.
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.
8.4.1 Basics
Computers share information over the Internet using a common language called TCP/IP. TCP/
IP, in turn, is a set of application protocols that perform specific functions. An “extension
number”, called the "TCP port" or "UDP port" identifies these protocols, such as HTTP
(Web), FTP (File Transfer Protocol), POP3 (E-mail), etc. For example, Web traffic by default
uses TCP port 80.
When computers communicate on the Internet, they are using the client/server model, where
the server "listens" on a specific TCP/UDP port for information requests from remote client
computers on the network. For example, a Web server typically listens on port 80. Please note
that while a computer may be intended for use over a single port, such as Web on port 80,
other ports are also active. If the person configuring or managing the computer is not careful, a
hacker could attack it over an unprotected port.
Some of the most common IP ports are shown in
IP, in turn, is a set of application protocols that perform specific functions. An “extension
number”, called the "TCP port" or "UDP port" identifies these protocols, such as HTTP
(Web), FTP (File Transfer Protocol), POP3 (E-mail), etc. For example, Web traffic by default
uses TCP port 80.
When computers communicate on the Internet, they are using the client/server model, where
the server "listens" on a specific TCP/UDP port for information requests from remote client
computers on the network. For example, a Web server typically listens on port 80. Please note
that while a computer may be intended for use over a single port, such as Web on port 80,
other ports are also active. If the person configuring or managing the computer is not careful, a
hacker could attack it over an unprotected port.
Some of the most common IP ports are shown in
8.4.2 Types of DoS Attacks
There are four types of DoS attacks:
1 Those that exploit bugs in a TCP/IP implementation.
2 Those that exploit weaknesses in the TCP/IP specification.
3 Brute-force attacks that flood a network with useless data.
2 Those that exploit weaknesses in the TCP/IP specification.
3 Brute-force attacks that flood a network with useless data.