ZyXEL Communications G.SHDSL.bis 4-port Security Gateway P-793H - Manual (Page 146)

P-793H User’s Guide
146 Chapter 9 Firewall Configuration
Figure 65 Firewall Example: Rules: MyService
9.9 Anti-Probing
If an outside user attempts to probe an unsupported port on your ZyXEL Device, an ICMP
response packet is automatically returned. This allows the outside user to know the ZyXEL
Device exists. The ZyXEL Device supports anti-probing, which prevents the ICMP response
packet from being sent. This keeps outsiders from discovering your ZyXEL Device when
unsupported ports are probed.
Internet Control Message Protocol (ICMP) is a message control and error-reporting protocol
between a host server and a gateway to the Internet. ICMP uses Internet Protocol (IP)
datagrams, but the messages are processed by the TCP/IP software and directly apparent to the
application user.
Refer to Section 8.1 on page 119 for more information.
Click Security > Firewall > Anti Probing to display the screen as shown.
Figure 66 Firewall > Anti Probing