Is it possible to "fake" being connected to a router?

Question

A friend of mine is taking a UNIX systems class and mentioned to me that when they take exams they do so on their computers. That is all students are using their own computer/laptop. Students are not being provided a computer by the professor. In an attempt to prevent cheating and googling of the answers, all student's are required to connect to a router that the professor has set up in order to take the exam. This router is not connected to the internet.

If anyone disconnects from the router during the exam time the professor then knows that they were potentially trying to use the internet. Apparently he has told his class that this system is "foolproof" and is so confident in its ability to prevent student network access he often leaves the room during the exam.

I admit that I'm not particularly well versed in this area of networking but theoretically couldn't this safeguard be defeated by using something resembling a man in the middle attack. You spoof a MAC address and IP and send that to the target router, which then thinks you are connected even though there is no real connection? Or is this problem network card based, where the vast majority of computers only have 1 wifi card and can therefore only do network related tasks for 1 network at a time.

Answer 1

Well, obviously it's not "foolproof". Depending on your capabilities, there are plenty of ways to cheat.

Your professor has a point in that your standard wireless network card won't simply support a simultaneous connection to multiple different APs, thus preventing your from using that particular interface for an Internet connection. (Although with some tinkering you could possibly alternate between networks without letting the professor's AP take notice by tweaking your driver to omit the layer-2 management frames that are supposed to notify the AP of your intent to dis-/reassociate.)

However, there are also easy workarounds:

• Build in a second network adapter (or plug in an external USB one, once the professor leaves) to connect to a network with Internet access. You can easily do this without interrupting your existing connection.
• Connect with your phone or another device instead of your real computer. On that device you can configure the broadcasted MAC address to match the one of your computer. This could fool your professor but probably wouldn't withstand a forensic investigation of the traffic.

• Use Bluetooth. Most laptops have built-in BT, so you could just tunnel your traffic via BT to a hidden device that itself is connected to the internet.

• Get creative. There are plenty of ways to bridge an apparent air gap. You might use your sound card to transmit data in a small range (or even your hard drive for that matter) - but then again you could also spend that time studying for the exam.

One effective countermeasure might be capturing every student's screen during the exam, but personally I find that very intrusive. Ultimately, if the professor allows students to use their own computers there will always be some way to prepare the devices to cheat.

Answer 2

You don't need to fake being connected to a router. The simplest way to ensure that you're detected as being connected to a router is to be genuinely connected to that router. That doesn't mean you're connected only to that router.

A $10 USB wifi adapter or a slightly more expensive 3G/4G adapter can connect a PC to the Internet, bypassing any other network connection that they might have. The PC would of course need to be configured carefully, make sure that it isn't forwarding packets between its connection to the Internet and its connection to the professor's router or the game would be up.

The only way for the professor to know that the students are cheating would be to retain full control over the computers, i.e. ensure that the students can't make changes to the network configuration and can't activate any hotplugged peripherals. And of course the professor should ensure that the students aren't discreetly using a mobile phone.

Answer 3

In addition to the existing answers: some laptops have built-in SIM card slots. My previous laptop had one which could only be accessed by removing the battery. You could connect the built-in wifi card to the wifi provided by the router, and use the mobile internet for your cheating. This has the advantages that there is no additional wifi network - which the professor could easily track down - and no dongle that the professor might find suspicious. On the downside, you need to have a laptop with that feature (or use a dongle which provides this feature, destroying one of the advantages).

Answer 4

Caution, may contain humour.

Yes, it's enough

Alright, now I got your attention.

Basically, I use an ontological argument: the fact that he is a professor who should know this kind of stuff, and is so sure, tells me that the room you are taking the test in has absolutely no possibility of WLAN or Mobile access. I.e., an underground room with lots of steel and very thick walls around.

I also deduce that the professor has verified, using all kinds of different smartphones/WLAN routers and different SIM cards (different providers), that not a single corner of the room allows any meaningful connection.

In this case, yes, he can be sure, because...

Physical connection

He can be sure that your ethernet port is and stays physically connected to his router. His router will log physical plugging/unplugging of ports (the lowest layer of the network stack - link level). There is nothing in the world you can do against it without it being very obvious. In far fetched theory (James Bond style) you could theoretically somehow screw with the cable - separate individual strands while it is connected, and connect some kind of quite involved electronic gadget with alligator clips that keep the link layer up while you disconnect your laptop.

But

We have to take more assumptions: it would be trivial for you to connect a USB-Ethernet-Adapter to your laptop and run that into some Ethernet port on the walls or on your desk which gives you internet access. Since the professor is a) knowledgeable and b) very sure of himself, this logically means that there are no such Ethernet ports available in the room.

This, and now comes the crux, means that everything he did was in vain. I.e., there was no reason to actually connect you to the router in the first place - if there is no Ethernet port available, there is no reason for you to "plug up" your laptop's port.

This, sadly, brings the whole beautiful thought building crumbling down. The professor is obviously having no clue, and everything is pointless.

Conclusion and outlook

As we look for only the best in all people, it is obvious to me that the professor is not having no clue. The point of the exercise is to detect which of the students is first to hack his protection. Those will obviously get bonus points (in the form of knowledge gained through the Internet access).

So it all makes sense. The professor is a brilliant genius who teaches you to question authority, not to blindly follow technical leaders, and think out of the box. Congratulations!

Answer 5

Let's just make your professor's router act up a bit.

You can use an ESP8266 to launch a de-auth attack that disconnects everyone from the router, basically tricking the professor to think there's something wrong with his router. https://hackaday.io/project/9333-weekend-on-the-dark-side

Another option for the same attack but without dedicated hardware, launch the attack from your laptop: http://hackaday.com/2011/10/04/wifi-jamming-via-deauthentication-packets/

Answer 6

A cellular modem? One can be installed inside the machine. Remembering an instructor who invited me to try to break into a server, I can't help wondering what this professor is really doing. Do you get a better mark if you defeat his system?

Answer 7

Well, this is definitely enough. When younger, we passed our exams (in a high school) each in our own room, with all books and other documents being available. The rationale for that was that if you needed to read a lesson to make an exercise, you would not have enough time to complete it.

You can certainly cheat the poor protection set up by the professor. But:

• it will certainly take some time, that will no longer be usable for completing the exam
• if you need to search on Internet to complete an exercise, you will spend too much time to be able to complete the exam
• there is a risk that you get caught while actually connected to internet. What do you think will happen after? You have willingly cheated on a exam, bypassing a security system. Chances are that you are simply excluded from the exam.

People have always tried to cheat for their exams, and those that always passed were the ones that simply learned enough to be able to answer without cheating. You may pass once by cheating, but if there are different tests for your examination, the risk of being caught is much too high IMHO.

That being said, it is indeed very easy to setup a second router with a USB cable to a smartphone...

Answer 8

The simplest solution would be to connect to your smart phone via blue tooth and connect to the internet that way. I'm ofc assuming your laptop has built in blue tooth, if it doesn't buy a blue tooth dongle.

Better yet, if he requires a physical ethernet connection to your laptop, just connect to your phone's wifi hotspot with your laptop's wifi card and skip blue tooth all together!