ZyXEL Communications P-660H-T1 v2, User Manual

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Chapter 9 Firewall Configuration
P-660H-Tx v2 User’s Guide
139
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 111 for more information.
Click Security > Firewall > Anti Probing to display the screen as shown.
Figure 73 Firewall: Anti Probing
SSH(TCP/UDP:22) Secure Shell Remote Login Program.
STRMWORKS(UDP:1558) Stream Works Protocol.
SYSLOG(UDP:514) Syslog allows you to send system logs to a UNIX server.
TACACS(UDP:49) Login Host Protocol used for (Terminal Access Controller Access
Control System).
TELNET(TCP:23) Telnet is the login and terminal emulation protocol common on the
Internet and in UNIX environments. It operates over TCP/IP networks.
Its primary function is to allow users to log into remote host systems.
TFTP(UDP:69) Trivial File Transfer Protocol is an Internet file transfer protocol similar
to FTP, but uses the UDP (User Datagram Protocol) rather than TCP
(Transmission Control Protocol).
VDOLIVE(TCP:7000) Another videoconferencing solution.
Table 43 Predefined Services (continued)
SERVICE DESCRIPTION