ZyXEL Communications P-661H Series, User Manual, Page: 150 / 383

P-661H/HW Series User’s Guide
150 Chapter 8 Firewalls
Figure 81 Smurf Attack
8.4.2.1 ICMP Vulnerability
ICMP is an error-reporting protocol that works in concert with IP. The following ICMP types
trigger an alert:
8.4.2.2 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.
Table 57 ICMP Commands That Trigger Alerts
5 REDIRECT
13 TIMESTAMP_REQUEST
14 TIMESTAMP_REPLY
17 ADDRESS_MASK_REQUEST
18 ADDRESS_MASK_REPLY
Table 58 Legal NetBIOS Commands
MESSAGE:
REQUEST:
POSITIVE:
VE:
RETARGET:
KEEPALIVE:
Table 59 Legal SMTP Commands
AUTH DATA EHLO ETRN EXPN HELO HELP MAIL NOOP
QUIT RCPT RSET SAML SEND SOML TURN VRFY