What You Need To Know About Firewall - ZyXEL Communications P-792H User Manual

Chapter 9 Firewalls
• Use the Threshold screen
the P-792H v2 uses to determine when to start dropping sessions that do not
become fully established (half-open sessions).

9.1.2 What You Need to Know About Firewall

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 P-792H v2, an
ICMP response packet is automatically returned. This allows the outside user to
know the P-792H v2 exists. The P-792H v2 supports anti-probing, which prevents
the ICMP response packet from being sent. This keeps outsiders from discovering
your P-792H v2 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.
DoS Thresholds
For DoS attacks, the P-792H v2 uses thresholds to determine when to drop
sessions that do not become fully established. These thresholds apply globally to
all sessions. You can use the default threshold values, or you can change them to
values more suitable to your security requirements.
Finding Out More
• See Section 9.1.3 on page 119
• See Section 9.5 on page 133
118
(Section 9.4 on page 129) to set the thresholds that
for an example of setting up a firewall.
for advanced technical information on firewall.
P-792H v2 User's Guide