Siphoning data on public and private WiFi

So you may remember I have been reviewing some cyber-thrillers in the past, and some of them have been pretty bad. After that I actually thought I could write one myself; after all, it couldn’t be as bad as Counting from Zero. Unfortunately the harsh reality is that I don’t know enough diverse people out there to build up new, interesting but most importantly realistic characters. So I shelved the project completely.

But at the same time, I spent a lot of time thinking of interesting things that may happen in a cyber-thriller that fit more into my world view — while Doctorow will take on surveillance, and Russinovich battles terrorists armed with Windows viruses, I would have put my characters in to deal with the more mundane variety of cyber criminals.

One of the things that I thought about is a variant on an old technique, called Wardriving. While this is not a new technique, I think there are a few interesting twists and it would be a little too interesting tool for low-lifers with a little (not a lot) of computer knowledge.

First of all, when wardriving started as what became a fad, the wireless networks out there were vastly unencryped and for the most part underutilized. Things changed, now thanks to WPA a simple pass-by scan of a network does not give you as much data, and changes in the way wireless protocols are implemented have, for a while, made the efforts hard enough.

But things changed over time, so what is the current situation? I have been thinking of how many things you could do with a persistent wardriving, but it wasn’t until I got bored out of my mind on a lounge at an airport that I was able to prove my point. On my own laptop, in a totally passive mode, invisible to any client on the network, a simple tcpdump or Wireshark dump would show a good chunk of information.

For the most part not something that would be highly confidential — namely I was not able to see anything being sent by the other clients of the network, but I was able to see most of the replies coming from the servers; just monitor DNS and clear-text HTTP and you can find a lot of information about who’s around you.

For instance I could tell that there was another person in the lounge waiting for the same flight as me — as they were checking the RTE website, and I doubt any person not Irish or not connected with Ireland would spend time there. Oh and the guy sitting in front of me was definitely Japanese, because once he sat down I could see the replies back from and a few more websites based in Japan.

Let me be clear, I was not doing that with the intention of doxxing somebody. I originally started tcpdump because one of my own servers was refusing me access — the lounge IP range is in multiple DNSBL, I was expecting the traffic on the network to be mostly viruses trying to replicate. What I found instead was that the access point is broadcasting to all connected clients the replies coming in for anyone else. This is not entirely common: usually you need to set your wireless card in promiscuous mode, and many cards nowadays don’t even let you do that.

But if this is the small fries of information I can figure out by looking at a tcpdump trace in a few minutes, you can imagine what you can find if you can sniff a network for a few hours. But spending a few hours tracing a network in the coffee shop at the corner could be suspicious. How can you make it less obvious? Well, here’s an interesting game, although I have not played it if not in my own stories’ drafts.

There are plenty of mobile WiFi devices out there — they take a SIM card and then project a WiFi signal for you to connect your devices to. I have one by Vodafone (although I use it with a bunch of different operators depending on where I’m traveling), and it is very handy, but while it runs Linux I did not even look for the option of rooting it. These are pretty common to find on eBay, second hand, because sometimes they essentially come free with the contract, and people update them fairly often as new features come up. Quite a few can run OpenWRT.

These devices come with a decent battery (mine lasts easily a whole day of use), and if you buy them second hand they are fairly untraceable (does anybody ever record the IMEI/serial number of the devices they sell?), and are ready to connect to mobile networks (although that’s trickier, the SIM is easier to trace.) Mine actually comes with a microSDHC slot, which means you can easily fit a very expensive 128GB microSD card if you want.

Of course it relies a lot on luck and the kind of very broad fishing net that makes it unfeasible for your average asshole to use, but there isn’t much needed — just a single service that shows you your plaintext password on a website, to match to an username, as most people will not use different passwords across services, with very few exceptions.

But let’s make it creepier – yes I’ll insist on making my posts about what I perceive to be a more important threat model than the NSA – instead of playing this on a random coffee shop at the corner, you are looking into a specific someone’s private life, and you’re close enough that you know or can guess their WiFi access point name and password, dropping one of these devices within the WiFi reach is not difficult at all.

The obvious question becomes what can you find with such a trace. Well, in no particular order you can tell the routine of a person quite easily by figuring out which time of the day they are at home (my devices don’t talk to each other that much when I’m not at home), what time they get up for work, and what time they are out of the door. You can tell how often they do their finances (I don’t go to my bank’s site every day, much less often the revenue’s). For some of the people out there you can tell when they have a private moment and what their interests are (yes I admit I went and checked, assuming you can only see the server response, you can still tell the title of the content that is being streamed/downloaded.) You can tell if they are planning a vacation, and in many cases where. You can tell if they are going to see a movie soon.

Creepy enough? Do I need to paint you a picture of that creepy acquaintance that you called in last week to help you set up your home theater, and to which you gave the WiFi password so he could Google up your provider’s setup guide?

How do you defend from this? Well, funnily enough a lot of the things people have been talking before the “Snowden Revelations” help a lo with this: HTTPS Everywhere and even Tor helps with this. While the latter gives you a different set of problems (it may be untraceable but it does not mean it’s secure!), it does obfuscate the data flow out of your network. It does not hide the traffic patterns (so you can still tell when people are in or not, when they wake up, and so on) but it does hide where you’re going, so that your private moments stay private. Unfortunately it is out of the reach of most people.

HTTPS is a compromise: you can’t tell exactly what’s going on, but if your target is going to YouPorn, you can still tell by the DNS reply. It does reduce the surface of attack considerably, though, and does not require that much technical knowledge on the client side. It’s for reasons like this that service providers should use HTTPS — it does not matter if the NSA can break the encryption, your creepy guy is not the NSA, but small parts of the creepy guy’s plan are thwarted by it: the logs can show the target visited the website of a movie theatre chain, but can’t show the replies from the server with the name of the branch or the movie that the target was interested in.

What is not helping us here, right now, with the creepy guys that are so easy to come by, is the absolute paranoia of the security and cryptography community right now. Dark email? Secure text messaging? They are definitely technologies that need to be explored and developed, but they should not be the focus of the threat model for the public. In this, I’m totally agreeing with Mickens.

I was (and a bit am) scared about writing about this, it makes me feel creepy. It gives a very good impression of how easy it is to abuse a bit of technical knowledge to become a horrible person. And with the track record of the technical circle in the past few years, it does scare the hell out of me, pardon the language.

While the rest of the security and technical community keep focusing on the ghost of the NSA, my fears are in the ease of everyday scams and information leaks. I was not surprised of what the various secret agencies out there wanted to do, after all we’ve seen the movies and the TV series. I was surprised of a few of the tools and reaches, but not the intentions. But the abuse power? There’s just as much of it outside of the surveillance community, it’s just that the people who know don’t care – they focus on theoretical problems, on the Chief World Systems, because that’s where the fun and satisfaction is – and the people who are at risk either believe everything is alright, or everything is not alright; they listen to what the media has to say, and the media never paints useful pictures.

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