ZyXEL 202H 91-003-194003B User Manual

P-202H Plus v2 User’s Guide

81

Chapter 8 Firewalls

Figure 29   Smurf Attack

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

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. 

Table 18   ICMP Commands That Trigger Alerts

5

REDIRECT

13

TIMESTAMP_REQUEST

14

TIMESTAMP_REPLY

17

ADDRESS_MASK_REQUEST

18

ADDRESS_MASK_REPLY

Table 19   Legal NetBIOS Commands

MESSAGE:

REQUEST:

POSITIVE:

VE:

RETARGET:

KEEPALIVE:

Table 20    Legal SMTP Commands

AUTH

DATA

EHLO

ETRN

EXPN

HELO

HELP

MAIL

NOOP

QUIT

RCPT

RSET

SAML

SEND

SOML 

TURN

VRFY