ZyXEL Communications Internet Security Gateway ZyWALL 2 Series - Manual (Page 315)

ZyWALL 2 Series User’s Guide
Remote Management Screens 17-29
Table 17-8 Security
LABEL DESCRIPTION
Respond to Ping
on
The ZyWALL will not respond to any incoming Ping requests when Disable is
selected. Select LAN to reply to incoming LAN Ping requests. Select WAN to reply to
incoming WAN Ping requests. Otherwise select LAN & WAN to reply to both incoming
LAN and WAN Ping requests.
Do not respond
to requests for
unauthorized
services
Select this option to prevent hackers from finding the ZyWALL by probing for unused
ports. If you select this option, the ZyWALL will not respond to port request(s) for
unused ports, thus leaving the unused ports and the ZyWALL unseen. By default this
option is not selected and the ZyWALL will reply with an ICMP Port Unreachable
packet for a port probe on its unused UDP ports, and a TCP Reset packet for a port
probe on its unused TCP ports.
Note that the probing packets must first traverse the ZyWALL 's firewall mechanism
before reaching this anti-probing mechanism. Therefore if the firewall mechanism
blocks a probing packet, the ZyWALL reacts based on the firewall policy, which by
default, is to send a TCP reset packet for a blocked TCP packet. You can use the
command "sys firewall tcprst rst [on|off]" to change this policy. When the firewall
mechanism blocks a UDP packet, it drops the packet without sending a response
packet.
Apply Click Apply to save your customized settings and exit this screen.
Reset Click Reset to begin configuring this screen afresh.