ZyXEL Communications eircom D1000, User Manual

Page: 149 / 226

147
eircom D10
00 modem User’s Guide
1 3
Firewall
13.1 Overview
This chapter shows you how to enable the Device firewall. Use the firewall to protect your Device
and network from attacks by hackers on the Internet and control access to it. The firewall:
• allows traffic that originates from your LAN computers to go to all other networks.
• blocks traffic that originates on other networks from going to the LAN.
• blocks SYN and port scanner attacks.
By default, the Device blocks DDOS, LAND and Ping of Death attacks whether the firewall is enabled
or disabled.
The following figure illustrates the firewall action. User A can initiate an IM (Instant Messaging)
session from the LAN to the WAN (1). Return traffic for this session is also allowed (2). However
other traffic initiated from the WAN is blocked (3 and 4).
Figure 99
Default Firewall Action
LAN
A
WAN
1
2
3
4
13.1.1 What You Can Do in the Firewall Screens
• Use the General screen ( Section 13.2 on page 149 ) to select the firewall protection level on the
Device.
• Use the Default Action screen ( Section 13.3 on page 150 ) to set the default action that the
firewall takes on packets that do not match any of the firewall rules.
• Use the Rules screen ( Section 13.4 on page 151 ) to view the configured firewall rules and add,
edit or remove a firewall rule.
• Use the DoS screen ( Section 13.5 on page 156 ) to set the thresholds that the Device uses to
determine when to start dropping sessions that do not become fully established (half-open
sessions).