ZyXEL Communications 2WG - Manual (Page 229)

ZyWALL 2WG Support Notes
All contents copyright (c) 2006 ZyXEL Communications Corporation.
229
B04. What kind of firewall is the ZyWALL?
1. The ZyWALL's firewall inspects packets contents and IP headers. It is applicable to all protocols,
that understands data in the packet is intended for other layers, from network layer up to the
application layer.
2. The ZyWALL's 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.
3. The ZyWALL's 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.
4. The ZyWALL's firewall is fast. It uses a hashing function to search the matched session cache
instead of going through every individual rule for a packet.
5. The ZyWALL's firewall provides email service to notify you for routine reports and when alerts
occur.
B05. Why do you need a firewall when your router has packet filtering and NAT built-in?
With the spectacular growth of the Internet and online access, companies that do business on the Internet
face greater security threats. Although packet filter and NAT restrict access to particular computers and
networks, however, for the other companies this security may be insufficient, because packets filters
typically cannot maintain session state. Thus, for greater security, a firewall is considered.
B06. What is Denials of Service (DoS)attack?
Denial of Service (DoS) attacks are aimed at devices and networks with a connection to the Internet.
Their goal is not to steal information, but to disable a device or network so users no longer have access to
network resources.
There are four types of DoS attacks:
1. Those that exploits bugs in a TCP/IP implementation such as Ping of Death and Teardrop.
2. Those that exploits weaknesses in the TCP/IP specification such as SYN Flood and LAND
Attacks.
3. Brute-force attacks that flood a network with useless data such as Smurf attack.
4. IP Spoofing