Dos Thresholds; Threshold Values; Table 70 Firewall: Anti Probing - ZyXEL Communications 802.11g ADSL 2+ 4-Port Security Gateway HW-D Series User Manual

P-662H/HW-D Series User's Guide
The following table describes the labels in this screen.

Table 70 Firewall: Anti Probing

LABEL
Respond to PING
on
Do Not Respond to
Requests for
Unauthorized
Services.
Apply
Cancel

11.10 DoS Thresholds

For DoS attacks, the ZyXEL Device uses thresholds to determine when to drop sessions that
do not become fully established. These thresholds apply globally to all sessions.
You can use the default threshold values, or you can change them to values more suitable to
your security requirements.
Refer to Section 11.10.3 on page 200

11.10.1 Threshold Values

Tune these parameters when something is not working and after you have checked the firewall
counters. These default values should work fine for most small offices. Factors influencing
choices for threshold values are:
• The maximum number of opened sessions.
• The minimum capacity of server backlog in your LAN network.
• The CPU power of servers in your LAN network.
• Network bandwidth.
• Type of traffic for certain servers.
If your network is slower than average for any of these factors (especially if you have servers
that are slow or handle many tasks and are often busy), then the default values should be
reduced.
198
DESCRIPTION
The ZyXEL Device does not respond to any incoming ping requests when Disable
is selected. Select the interface which you want to reply to incoming ping requests.
Select this option to prevent hackers from finding the ZyXEL Device by probing for
unused ports. If you select this option, the ZyXEL Device will not respond to port
request(s) for unused ports, thus leaving the unused ports and the ZyXEL Device
unseen. By default this option is not selected and the ZyXEL Device 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 ZyXEL Device's firewall
mechanism before reaching this anti-probing mechanism. Therefore if the firewall
mechanism blocks a probing packet, the ZyXEL Device reacts based on the
corresponding firewall policy to send a TCP reset packet for a blocked TCP packet
or an ICMP port-unreachable packet for a blocked UDP packets or just drop the
packets without sending a response packet.
Click Apply to save your changes back to the ZyXEL Device.
Click Cancel to begin configuring this screen afresh.
to configure thresholds.
Chapter 11 Firewall Configuration