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Chapter 14 Firewall
P-2612HNU-Fx User’s Guide
204
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.
Anti-Probing
If an outside user attempts to probe an unsupported port on your ZyXEL Device,
an ICMP response packet is automatically returned. This allows the outside user to
know the ZyXEL Device exists. The ZyXEL Device supports anti-probing, which
prevents the ICMP response packet from being sent. This keeps outsiders from
discovering your ZyXEL Device when unsupported ports are probed.
ICMP
Internet Control Message Protocol (ICMP) is a message control and error-reporting
protocol between a host server and a gateway to the Internet. ICMP uses Internet
Protocol (IP) datagrams, but the messages are processed by the TCP/IP software
and directly apparent to the application user.
Finding Out More
See Section 14.3 on page 206 for advanced technical information on firewall.
14.2 The Firewall Screen
Use this screen to enable service blocking and to maintain the list of services you
want to block. To access this screen, click Security > Firewall.