ZyXEL Communications G-2000 Plus - Manual (Page 185)

ZyAIR G-2000 Plus User’s Guide
Chapter 14 Firewalls 184
Figure 77 Smurf Attack
14.4.2.1 ICMP Vulnerability
ICMP is an error-reporting protocol that works in concert with IP. The following ICMP types
trigger an alert:
Table 59 ICMP Commands That Trigger Alerts
5 REDIRECT
13 TIMESTAMP_REQUEST
14 TIMESTAMP_REPLY
17 ADDRESS_MASK_REQUEST
18 ADDRESS_MASK_REPLY
14.4.2.2 Traceroute
Traceroute is a utility used to determine the path a packet takes between two endpoints.
Sometimes when a packet filter firewall is configured incorrectly an attacker can traceroute
the firewall gaining knowledge of the network topology inside the firewall.
Often, many DoS attacks also employ a technique known as "IP Spoofing" as part of their
attack. IP Spoofing may be used to break into systems, to hide the hacker's identity, or to
magnify the effect of the DoS attack. IP Spoofing is a technique used to gain unauthorized
access to computers by tricking a router or firewall into thinking that the communications are
coming from within the trusted network. To engage in IP spoofing, a hacker must modify the
packet headers so that it appears that the packets originate from a trusted host and should be
allowed through the router or firewall. The ZyAIR blocks all IP Spoofing attempts.