[dumb it down]
There is a kind of alert in the computer security world, called a CVE, or Common Vulnerabilities and Exposure. These cover all manner of exploitable holes in software or hardware that hackers can exploit. By seeing if there are any known and unpatched vulnerabilities in the network card itself in that system, it allows us to quickly and decisively attack that system and gain access.
Now-- Modern network cards are actually small computers in and of themselves. They have a processor, memory, and a core program. It is possible to compromise these in some circumstances. Most modern network cards are bus mastering, which is a form of direct memory access. This allows the card to write on memory without the system's CPU being involved. This allows incoming packet data to be fed directly to software running in the computer, and do so very efficiently. It also means that if the network interface card is compromised, it can write over memory it owns inside the computer. The software that handles the network card lives in kernel memory, which is privileged. This means a compromised NIC is able to function as a vector of attack to own a computer's security from the inside.
See for instance, this story about some broadcomm fast ethernet controllers, and a proof of concept malicious firmware that does exactly this kind of thing.
(Yes I know, it's a "Register" article. Yes. Yes I know. Please dont tell me how unreliable a source it is, I already know.)
http://www.theregister.co.uk/2010/11/23/network_card_rootkit/So, the suggestion is:
Is there a way we can talk to the internet?
IF YES:
OK, look up the hardware specs of the locked down computer, so we know what hardware is in it.
After looking up the hardware, check for any CVEs on it.
IF there are any CVEs on the network card, exploit them to PWN the locked down computer
If any of those are a NO, then we have to try something else.