Dos Thresholds; Threshold Values; Table 58 Firewall: Anti Probing - ZyXEL Communications P-660HW-T - V2 User Manual

P-660HW-T v2 User's Guide
The following table describes the labels in this screen.

Table 58 Firewall: Anti Probing

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

10.10 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 10.10.3 on page 168

10.10.1 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.
166
DESCRIPTION
The ZyXEL Device does 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.
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 to the ZyXEL Device.
Click Cancel to begin configuring this screen afresh.
to configure thresholds.
Chapter 10 Firewall Configuration