Title:

Shared Software Firewall with NAT for Multiple Public IP Addresses

Objective:

The goal of this project is to create a working software-based firewall that 
is shared by all computers on a network. Besides providing protection against 
hackers and outside Internet traffic, it will use NAT (Network Address 
Translation) to convert public IP addresses into private IP addresses and 
vice-versa. Also, it will be able to assign each computer on the network its 
own unique public IP address. Hackers trying to get into a computer through 
its public IP address will be unable to.

Justification:

Currently firewalls are designed to protect whole networks of computers (even 
if the network consists of just one computer), and each of these computers has 
their own private IP address. Every computer on the network itself uses the 
same public IP address; whichever public address an ISP (Internet service 
provider) has given to the router. Certain applications online (a game, for 
instance) do not allow multiple instances of the same public IP address. This 
poses a problem for networked computers sharing a public address. This firewall
will illiminate that problem, without one having to purchase an expensive 
router that provides multiple public IP support. Another added benefit is that 
this program will function as a firewall as well, monitoring activity and 
preventing those outside the network to access the network. Most software 
firewalls do not provide good protection. However, as this firewall will be 
shared by all computers on the network, it alone can monitor all traffic from 
all computers, and by improving on the methods of other firewalls, can 
potentially provide better protection. Because all of this is software based, 
it also will be much cheaper than a router and hardware firewall.

Description:

A firewall is simply a program that monitors incoming and outgoing packets 
through a computer's ports, so the project will require writing a program that 
monitors all outgoing packets from all computers. Next, NAT has to be 
programmed into the firewall as a additional feature. Furthermore, the program 
needs to be able to assign multiple public IP addresses. These addresses will 
have to be obtained from a service provider. At least two computers will be 
needed, however more is preferable.

Limitations:

Time will most likely be a significant problem with this project, because of 
the many steps required to put it all together. My understanding of how IP 
addresses are assigned and how ports are monitored, my understanding of NAT, 
and my understanding of how a router assigns an IP address will also be 
limiting. Technical constraints include not having the correct programming 
tools to be able to create the software neccessary to perform all of the tasks 
mentioned.