Security


As wireless 802.11 networks grows in popularity the number of insecure private and business networks skyrockets. Setting up a small hotspot is usually a matter of plugging in the wireless Access Point (AP) and you’ll have full access. This unfortunately means that everyone else has too, unless you know what you’re doing. As a natural consequence of this, there are a lot of myths out there on how you can keep the Evildoers off your network. Most of them have a base in reality, but if you don’t have all the facts they can give you a false sense of security as they might not be as bullet proof as they seem. Let’s go through some of them Mythbusters style:

Adding a MAC filter will let you decide which computers get to connect

MAC addresses are supposed to be the physical address of your computer’s (or AP’s) network adapters. Letting the AP have a list of physical cards which are allowed to connect seems like a good idea. Unfortunately MAC addresses are a) always transmitted in the open regardless of any encryption, and b) can be overridden in a lot of configurations. In other words, an attacker can listen for what MAC addresses are connected to the network, and then assume one of these identities. It would be best for the attacker to find a MAC which either leaves the network or is generating little traffic, since that computer (or strictly speaking the network adapter) of the “victim” and the attacker will be one and the same as far as the AP is concerned. Traffic bound for one of them will be received by both with ensuing messiness.

Conclusion: Busted! It will keep your random bypasser from connecting to the net, but won’t stop anyone really wanting in.

Setting the AP to not broadcast the SSID will keep people not knowing what it is from connecting

While knowing the Service Set ID is necessary to connect to a wlan, it’s not really a secret. Like the MAC addresses it’s transmitted in the open without any encryption, but unlike the MAC it’s not transmitted with every packet. Instead it’s included in the handshake when someone connects to the network, so you’ll be safe as long as no legal users ever connect to you network. Clever.

Conclusion: Busted! Again, it’ll keep the random jokers away but that’s about it.

WEP encryption is of no use

Cracking a WEP key doesn’t take much time in a network with a lot of traffic, and with packet injection techniques an attacker can even generate the traffic necessary for the crypto analysis to work without really being part of the network. There are however two upsides to WEP encryption as opposed to the two previous methods. 1) Cracking the wep key is without a doubt BREAKING into the network in a (il)legal sense, and 2) you won’t be transmitting your emails and surfing habit to anyone that might be passing and not inclined to crack the key.
Conclusion: Busted! It’s useless in the same way that locking your front door is useless if you’ve got windows in your house. Not the perfect analogy since someone bashing in a window can’t remain undetected.

WEP: Breakable but not completely without use


WPA2 is better than WPA

While WPA is an attempt to patch up the gaping security holes in WEP and still run on old hardware, WPA2 is rebuilt from the ground up with heftier encryption and message authentication using the AES algorithm which at the present has no known theoretical weaknesses. Since it had to be designed to run on old hardware WPA’s TKIP encryption and “Michael” authentication algorithms are inherently weaker, but no practical attacks have to my knowledge been suggested.

Conclusion Confirmed! If your hardware supports WPA2, there are no reasons not to choose it over WPA. However, there’s no need to panic just yet if it doesn’t.

You can’t touch me! I’m using WPA(2)!

While there are no known weaknesses (at least exploitable ones) in the system or encryption primitives, you need to realize that no system is stronger than its secrets. Most home users and small business are probably using WPA(2) in Pre Shared Key (PSK) mode, where the security is based on the supplicants knowing a secret key or a passphrase which is manually entered in the AP and the clients. This secret is then used to set up a common encryption key during the handshake between the client and AP. However, this process is part of the standard and well documented, the handshake can be recorded by an attacker using a standard packet sniffer and the only actual secret is the passphrase. This means that if a handshake is recorded and the passphrase is weak because it’s subject to a dictionary attack, the whole system falls apart. In other words, your super secret WPA2 network with super secret passphrase “Volvo” might very well take less time to crack than your average WEP based wlan.

Conclusion: If you don’t know what you’re doing: Busted!

You can’t touch me! I’m using WPA(2) in Enterprise mode with none of that shared key nonsense!

While an attacker might well be powerless today, there’s nothing stopping him from recording all the traffic for future analysis if he’s really determined. If your data is so sensitive that you cannot possibly accept that the data you transfer today might be decrypted 5 years into the future when a new weakness with today’s system is discovered you really shouldn’t be broadcasting it. That’s the key word right there – you are BROADCASTING your secrets in the hope that no one ever will be able to decrypt them. If you think that sounds like a bad idea, I would recommend sticking to the good old cables as of now, or at least use some form of upper level encryption like VPN and pray that that too will stay infallible.

Conclusion: As of right now, it’s Confirmed. If you’re willing to bet your secrets that it will remain confirmed forever and you don’t have any attackers that are very patient, then there’s nothing to worry about in the wlan department.

That’s it for now. While this might lack the explosions, walrus mustaches and the occasional beautiful women of the real Mythbusters, you’ve got to admit that wireless mythbusting is far more fun! For the whole family!

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SecuROM and Star Force are two of the more popular forms of "copy protection" schemes for computer games. The system is based on making you insert the correct DVD or CD each time you want to launch the game, and SecuROM's or StarForce's task is to make it harder to make a copy or image of the original media which stands up to validation. Fair enough. DVD-ROM is fast becomming a horribly inefficient, expencive and archaic way of content distribution, so I guess a horribly inefficient, expencive (in terms of usability) and archaic way of authentication is just fitting.

However, it stops beeing fine when my legal games stop working as a result of a broken "copy protection" scheme. The DVD-unit in my PC is a Samsung TS-H552U DVD Burner which is less than a year old. All other DVD-ROMs work just fine, but it runs it to a lot of problems just trying to read the "copy protected" DVDs. I've had some problems previously with Splinter Cell 3: Chaos Theory, which uses StarForce v3 (3.4.71.19) according to gamecopyworld. However, the real problems didn't show up until I bought Hitman: Blood Money, which uses SecuROM v7 (v7.00.00.0018). When I insert the DVD, 9 out of 10 times it won't be able to recognice the DVD at all. You can hear it starting to spin the disc slowly, and then resetting the laser position ad infinitum.

zum zum

…zum zum wock-wack……zum zum wock-wack……zum zum wock-wack……zum zuuum wock-wack……zum zum wock-wack……zum zum wock-wack……zum zuum wock-wack….

That won't get on your nerves.

End result: A "copy protected" game where the legal copy is probably harder to use than an illegal one. Nice going, people.

When you do manage actually play the game, Hitman: Bloody money is a pretty amusing in a Léon sort of way. You're obviously a hitman, and after each mission you get a fake newspaper report about the hit with phrases like "It concerns the authorities that all of the victims were brutally excecuted by shots to the head." According to violent computer game zealot Jack Thompson you have to be a computer gamer or a hitman to shoot people in the face. Well Jack, that might be true. It's not becauce of the violence in the video games however, but having to wade through the layers of incomptance that is "copy protection" every time you try to start the game would send Mother Theresa over the edge.

…zum zum wock-wack…

A while back I got called on my cell phone by some rather unpleasant saleswoman who wouldn’t take no for an answer. Luckily, it’s possible to stop this sort unsolicited advertizing in Norway by registering in the Brønnøysund Register Centre’s “Central Marketing Exclusion Register“. However, much to my surprise, the online registration didn’t require more than my Norwegian social security number (ssnr) as an identification. Now, why is this a bad idea? Isn’t your ssnr supposed be your identification number and a secret? Well, your ssnr is secret, but ssnrs as a whole isn’t. The Norwegian ssnr is 11 digits, the first 6 is the persons birthday and -year (ddmmyy), the next 3 is basically a counter over the births that specific day (which also acts as a gender flag since women are given even numbers and men odd) and the last two a checksum. In other words, it’s easy to compute random valid Norwegian ssnrs.

I’ve written a small Java ssnr-calculator as a proof of concept. It’ll calculate about 80 valid ssnrs for a given date. The text parsing is a bit basic, so I can only guarantee valid ssnrs for actual dates between 1900 and 1999. Now, before you get any fancy ideas, logging onto the system with someone else’s ssnr might as far as I know be considered a crime since it can be interpreted as identity theft or something else entirely. And even if it isn’t illegal you really shouldn’t. Just don’t.

This means that while it may not be trival to pin any ssnr to a specific person, it is trivial to find a ssnr belonging to some random Norwegian. Thus, it’s possible for an attacker generate valid ssnrs and log onto the system as those poor sods and potentially change their status. A determined attacker can undermine the whole system by generating a large number of ssnrs and using a botnet and some patience change a large number of entries. I’m sure the good folks in Brønnøysund has some nifty system logs and intrusion detection systems, but given enough time and bots for the attack the poisoned entries could be made pretty hard to spot.

Now, this isn’t the most critical of systems. To put it into perspective the Norwegian Internet Banks had similar security holes making it possible for an attacker to log onto random accounts a few years back. The system is never the less unnecessarily vulnerable, and can be taken down. However, there is an easy fix. As mentioned it’s relativly hard to pin a ssnr to a specific person or the other way around*, so if the registration process asked for your name in addition to your snnr, the possibility of a large scale attack like this would be thwarted with miniumum inconvenience to the normal users. Life can be easy.

The Brønnøysund Register Centre was informed of the weakness a week before this post.

*It’s actually easier than one would think. In 2002, there was 55400 births giving an average of 150 births a day. Thus, if you know the persons birthday and -year and its sex you’ll end up with about 75 possibilites, and expect to find the correct one in 32.5 attempts on average. Still, way too complex for a large scale attack on a system like this. You can read more about the Norwegian social security numbers at matematikk.org.