ZyXEL Communications P-660HN-51 - CHAPTER 10 Firewall; 10.1 Overview; 10.1.1 What You Can Do in this Chapter

P-660HN-51 User’s Guide
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CHAPTER 10
Firewall
10.1 Overview
This chapter shows you how to enable and configure the Zyxel Device firewall. Use the firewall to protect
your Zyxel Device and network from attacks by hackers on the Internet and control access to it. By
default 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.
The following figure illustrates the default 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 57 Default Firewall Action
10.1.1 What You Can Do in this Chapter
• Use the Firewall screen to configure the security level of the firewall on the Zyxel Device (Section 10.2
on page 128).
• Use the Protocol screen to add or remove predefined Internet services and configure firewall rules
(Section 10.3 on page 128).
• Use the Access Control screen to view and configure incoming/outgoing filtering rules (Section 10.4
on page 130).
10.1.2 What You Need to Know
SYN Attack
A SYN attack floods a targeted system with a series of SYN packets. Each packet causes the targeted
system to issue a SYN-ACK response. While the targeted system waits for the ACK that follows the SYN-
WAN
LAN
3
4
1
2
A