From UntangleWiki

Here's the steps I use to create new modules for various drivers on Untangle. Last tested on 7.2

This process has to be repeated twice, once for 486/686/i386 and once for amd64.

• Install system via ISO and configure.
• enable ssh (rm /etc/ssh/sshd_not_to_be_run)
• login via the terminal (set the password to passwd)
• now go sit at the relative comfort of your desk
• ssh to the box root@ip.addr.here
• create a file in /etc/apt/sources.list.d called dev.list with the following content:

deb http://ftp.us.debian.org/debian lenny main contrib non-free 

• run apt-get update
• run apt-get --yes install untangle-development-build
• on i386 system: run apt-get --yes install linux-headers-2.6.26-1-untangle-486 linux-headers-2.6.26-1-untangle-686
• on amd64 system: run apt-get --yes install linux-headers-2.6.26-1-untangle-amd64
• Immediately remove the file called /etc/apt/sources.list.d/dev.list

You should now be in a state where you can build the kernel modules as specified by the driver supplier

Exact instructions will vary based on the module, but the goal here is to build a new .ko file and copy it into the correct place in the /lib/modules hierarchy.