The quick an easy way to disable a network device in Linux.
At the University where I work we have a number of PCs used by Forensic Computing students which dual boot BackTrack and Windows 7. We needed Windows to be connected to the University network, but not BackTrack as the students use a local WLAN in the room for their forensic stuff and we need to keep them off the main network as besides the arsenal of tools which they have available, BackTrack is not joined to the Active Directory so all network activity would go unrecorded.
Disable in the BIOS
Whether or not this is practical depends upon your requirements and the option being available in your BIOS and you would need to ensure that the BIOS has a password set to prevent anyone from switching it back on. In my scenario this would also disable the NIC for Windows, so it would not be of any use to me.
Blacklist The Driver Module
Firstly, you need to determine what the driver is. To do this, open a terminal and run the command:
lshw -C network|more
This will display a load of information about your network device/s. Somewhere in the output you will see module=drivername in my case the Intel onboard NIC driver was module=e1000e
Once you have identified the driver name open /etc/modprobe.d/blacklist.conf
At the bottom of the file add the following line (this uses my driver module (e1000e) as an example, just replace it with the module name of yours)
Reboot for the blacklist to take effect. From now on whenever Linux boots, the kernel will not load the driver for the NIC.