User's Manual

Chapter 14 Firewall 153
RFC 4890 SPEC Traffic
RFC 4890 specifies the filtering policies for ICMPv6 messages. This is important for protecting
against s
ecurity threats including DoS, probing, redirection attacks and renumbering attacks that
can be carried out through ICMPv6. Since ICMPv6 error messages are critical for establishing and
maintaining communications, filtering policy focuses on ICMPv6 informational messages.
Anti-Probing
If an outside user attempts to probe an unsupported port on yo
ur Device, an ICMP response packet
is automatically returned. This allows the outside user to know the Device exists. The Device
supports anti-probing, which prevents the ICMP response packet from being sent. This keeps
outsiders from discovering your Device when unsupported ports are probed.
ICMP
Internet Control Message Protocol (ICMP) is a message contr
ol 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 Device uses thresholds to determine when to drop sessions that do not
b
ecome 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.
14.2 Firewall General Screen
Use this screen to select the firewall protection level on the Device. Click Security > Firewall >
General to display the following screen.
Figure 99 Secu
rity > Firewall > General