ZyXEL Communications p-2612HNU-FX User Manual

Chapter 14 Firewall

P-2612HNU-Fx User’s Guide

Denials of Service (DoS) attacks are aimed at devices and networks with a 
connection to the Internet. Their goal is not to steal information, but to disable a 
device or network so users no longer have access to network resources. The 
ZyXEL Device is pre-configured to automatically detect and thwart all known DoS 
attacks.

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. 

 for advanced technical information on firewall.

Use this screen to enable service blocking and to maintain the list of services you 
want to block. To access this screen, click Security > Firewall.