Final Examination Data Communication and Networks ...

{10{
Question 9
Dene the role of a rewall and draw a diagram that shows where a rewall should
be positioned with relation to protecting a local network. In dening the role of a
rewall, you should discuss the techniques that a rewall uses at dierent levels to
prevent external attacks on the network and control trac ow through the rewall.
[6]
SOLUTION
The solution will show a local area network structure and the rewall as the single
interface point or gateway to the outside world.
The characterisation of rewall activity will probably touch on a majority of the following
points.
[2]
denying connection requests to known ports, such as ftp, sendmail on hosts within
the local network.
packet ltering based on keywords or encryption status.
suspicious packet trac patterns that represent denial of service orpacket spoong
attacks on local hosts from external IP addresses.
an exceptional answer might note that wireless networking often bypasses rewalls
and represents a possible security hole.
[4]
OVER/