Firewall - ZyXEL Communications AX Series User Manual

Chapter 19 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.
DoS Thresholds
For DoS attacks, the Zyxel Device 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.
DDoS
A DDoS attack is one in which multiple compromised systems attack a single target, thereby causing
denial of service for users of the targeted system.
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.
LAND Attack
In a LAND attack, hackers flood SYN packets into the network with a spoofed source IP address of the
target 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.
Ping of Death
Ping of Death uses a 'ping' utility to create and send an IP packet that exceeds the maximum 65,536
bytes of data allowed by the IP specification. This may cause systems to crash, hang or reboot.
SPI
Stateful Packet Inspection (SPI) tracks each connection crossing the firewall and makes sure it is valid.
Filtering decisions are based not only on rules but also context. For example, traffic from the WAN may
only be allowed to cross the firewall in response to a request from the LAN.

19.2 Firewall

Use the firewall to protect your Zyxel Device and network from attacks by hackers on the Internet and
control access to it.
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