ZyXEL ADSL Prestige 2602R-61 VoIP 91-006-024004B Manual Do Utilizador

Prestige 2602R Series User’s Guide

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Chapter 12 Firewalls

• Always shred confidential information, particularly about your computer, before 

throwing it away. Some hackers dig through the trash of companies or individuals for 
information that might help them in an attack.

Below are some comparisons between the Prestige’s filtering and firewall functions.

• The router filters packets as they pass through the router’s interface according to the filter 

rules you designed.

• Packet filtering is a powerful tool, yet can be complex to configure and maintain, 

especially if you need a chain of rules to filter a service.

• Packet filtering only checks the header portion of an IP packet.

• To block/allow LAN packets by their MAC addresses.
• To block/allow special IP packets which are neither TCP nor UDP, nor ICMP packets.
• To block/allow both inbound (WAN to LAN) and outbound (LAN to WAN) traffic 

between the specific inside host/network "A" and outside host/network "B". If the filter 
blocks the traffic from A to B, it also blocks the traffic from B to A. Filters can not 
distinguish traffic originating from an inside host or an outside host by IP address.

• To block/allow IP trace route.

• The firewall inspects packet contents as well as their source and destination addresses. 

Firewalls of this type employ an inspection module, applicable to all protocols, that 
understands data in the packet is intended for other layers, from the network layer (IP 
headers) up to the application layer.

• The firewall performs stateful inspection. It takes into account the state of connections it 

handles so that, for example, a legitimate incoming packet can be matched with the 
outbound request for that packet and allowed in. Conversely, an incoming packet 
masquerading as a response to a nonexistent outbound request can be blocked.

• The firewall uses session filtering, i.e., smart rules, that enhance the filtering process and 

control the network session rather than control individual packets in a session.

• The firewall provides e-mail service to notify you of routine reports and when alerts 

occur.

• To prevent DoS attacks and prevent hackers cracking your network.