Network Attacks and Defenses

Packet Filtering and Inspection  ◾  271

7.8   Chapter Summary

An enterprise with an intranet that allows its workers to access

the wider Internet installs a firewall to prevent outsiders from

accessing its own private data resources and for controlling

what outside resources its own users have access to. Basically,

a firewall examines each network packet to determine

whether or not to forward it toward its destination. Therefore,

firewalls play an important role in the enforcement of access

control policies in contemporary networks.

This chapter discussed a series of hands-on exercises about

filtering rules implementation for basic security policies, filter-

ing of services running on nonstandard TCP and UDP ports,

verification of the consistency and ...