ZyXEL Communications P-334 - Manual (Page 149)

Prestige 334 User’s Guide
Chapter 13 Remote Management Screens 148
Do not respond to
requests for
unauthorized
services
Select this option to prevent hackers from finding the Prestige by probing for
unused ports. If you select this option, the Prestige will not respond to port
request(s) for unused ports, thus leaving the unused ports and the Prestige unseen.
By default this option is not selected and the Prestige 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 Prestige's firewall mechanism
before reaching this anti-probing mechanism. Therefore if the firewall mechanism
blocks a probing packet, the Prestige 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.
Table 44 Security
LABEL DESCRIPTION