How can I run a program in OS's kernel mode?

Question

I want to design a custom firewall for my internet security. But I think it will require the kernel mode to run! Is it true? Even if it isn't how can I write a program which runs in kernel mode?

Answer 1

Ig your on LINUX, you just "su" the user to use kernel mode. The user must be in the TRUSTED account to do so.
% /trusted/cat

Take a look at this article to run the program that you construct in kernel mode. It is just a simple patch:

http://www.linuxjournal.com/article/6516

If your designing a firewall to be in kernel mode, you could visit the link below for more details. To access Windows Kernel is tricky and almost unlikely