Prestige 662H/HW Series User’s Guide

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.

Figure 56 Smurf Attack

13.4.2.1 ICMP Vulnerability

ICMP is an error-reporting protocol that works in concert with IP. The following ICMP types trigger an alert:

Table 40 ICMP Commands That Trigger Alerts

5REDIRECT

13TIMESTAMP_REQUEST

14TIMESTAMP_REPLY

17ADDRESS_MASK_REQUEST

18ADDRESS_MASK_REPLY

13.4.2.2 Illegal Commands (NetBIOS and SMTP)

The only legal NetBIOS commands are the following - all others are illegal.

Table 41 Legal NetBIOS Commands

MESSAGE:

REQUEST:

POSITIVE:

VE:

RETARGET:

KEEPALIVE:

All SMTP commands are illegal except for those displayed in the following tables.

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Chapter 13 Firewalls