Software firewall concept

[sopharine]

Assuming we are talking about a single host network with wired connection to the WAN.

First. if a host wanted to access the Internet she would need NAT to translate its private address to a public address correct? Does that mean Windows 7 has NAT built-in?

Second. Before Windows XP Service Pack 2 came out, there were no firewall installed by default. How could a host with Windows version earlier than SP2 protect outside WAN from unsolicited accessing to its LAN?

Thank you for reading.

 

[Alejandro85]

To the first question, yes, you need some form of NAT to share an internet connection between many devices, so that all of them uses only one public IP address (on the WAN) but each with its own private IP (on the LAN). That's regardless of the operating system or the device.
Now, Win7 does include some precarious form of NAT built-in, though the internet sharing option. I never actually used that but it should be quite near to a NAT. Problem is that, for that to work properly, you need 2 network cards on the box, one connected to the WAN and other to the LAN, and Windows performs the NAT on those interfaces. Windows 2008 includes a more serious routing service too. Anyway, I think the best option for NAT is to buy a router and let it do NAT by hardware, often those devices perform much better and are far more secure.

Now for the second. WinXP before SP2 doesn't in fact includes a firewall built-in, so it can't protect on its own, but nothing impedes you from installing a third party firewall program that serves the same purpose. The Windows Firewall is just one choice of software firewall that you have, but many others exists. On XP SP2/3 or Win7, you can use that firewall, or just disable it and install another one if you like it more.