ZyXEL Communications P-335WT - Manual (Page 206)

P-335 Series User’s Guide
206 Chapter 15 Remote Management Screens
15.8 Configuring Security
To change your Prestige’s security settings, click REMOTE MGMT, then the Security tab.
The screen appears as shown.
If an outside user attempts to probe an unsupported port on your Prestige, an ICMP response
packet is automatically returned. This allows the outside user to know the Prestige exists.
Your Prestige supports anti-probing, which prevents the ICMP response packet from being
sent. This keeps outsiders from discovering your Prestige when unsupported ports are probed.
Figure 93 Security
The following table describes the labels in this screen.
Table 66 Security
LABEL DESCRIPTION
ICMP Internet Control Message Protocol 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.
Respond to Ping
on
The Prestige 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 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.