User guide

What Is a Firewall?
Chapter 2: The ZoneAlarm Firewall 11
Chapter 2
This chapter introduces the ZoneAlarm firewall and its advantages.
This chapter includes the following topics:
What Is a Firewall?.....................................................................................11
Security Requirements................................................................................12
Old Firewall Technologies .........................................................................12
Check Point Stateful Inspection Technology..............................................14
What Is a Firewall?
The most effective way to secure an Internet link is to put a firewall between the local
network and the Internet. A firewall is a system designed to prevent unauthorized access to
or from a secured network. Firewalls act as locked doors between internal and external
networks: data that meets certain requirements is allowed through, while unauthorized data
is not.
To provide robust security, a firewall must track and control the flow of communication
passing through it. To reach control decisions for TCP/IP-based services, (such as whether
to accept, reject, authenticate, encrypt, and/or log communication attempts), a firewall
must obtain, store, retrieve, and manipulate information derived from all communication
layers and other applications.
The ZoneAlarm Firewall