Figure 11-4 Smurf Attack; Table 11-2 Icmp Commands That Trigger Alerts; Table 11-3 Legal Netbios Commands; Table 11-4 Legal Smtp Commands - ZyXEL Communications Prestige 662HW Series User Manual

numerous hosts, this will create a large amount of ICMP echo request and response traffic. If a
hacker chooses to spoof the source IP address of the ICMP echo request packet, the resulting
ICMP traffic will not only clog up the "intermediary" network, but will also congest the network
of the spoofed source IP address, known as the "victim" network. This flood of broadcast traffic
consumes all available bandwidth, making communications impossible.

ICMP Vulnerability

ICMP is an error-reporting protocol that works in concert with IP. The following ICMP types trigger
an alert:
Illegal Commands (NetBIOS and SMTP)
The only legal NetBIOS commands are the following - all others are illegal.
All SMTP commands are illegal except for those displayed in the following tables.
AUTH DATA
QUIT RCPT
Firewalls

Figure 11-4 Smurf Attack

Table 11-2 ICMP Commands That Trigger Alerts

5 REDIRECT
13 TIMESTAMP_REQUEST
14 TIMESTAMP_REPLY
17 ADDRESS_MASK_REQUEST
18 ADDRESS_MASK_REPLY

Table 11-3 Legal NetBIOS Commands

MESSAGE:
REQUEST:
POSITIVE:
NEGATIVE:
RETARGET:
KEEPALIVE:

Table 11-4 Legal SMTP Commands

EHLO ETRN EXPN
RSET SAML SEND
Prestige 662HW Series User's Guide
HELO HELP MAIL
SOML TURN VRFY
NOOP
11-5