Why MAC address filtering doesn’t help security

The other question that came out of my recommended DD-WRT settings was why not filter MAC addresses. I hate to be flip, but MAC address filtering doesn’t help, so why bother?

The reason is because your MAC addresses are broadcast as part of the network traffic, and it’s unencrypted. So your MAC addresses aren’t any secret at all. So it doesn’t do any good. One could argue it doesn’t do any harm. But it adds an extra step every time you put something on your wireless network. Why go to the inconvenience if you don’t gain anything from it?

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Recommended DD-WRT settings

I’ve been asked a few times now for my recommended DD-WRT settings, or at least my good-enough settings. I think that’s a great idea, so I’ll walk through how I configure a DD-WRT router. Follow these steps and I can almost guarantee you’ll have the most secure network on your block.

For the purposes of this tutorial, I am going to assume you are configuring DD-WRT as your primary router.

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How to be a hero next Christmas (or your next family get-together)

My mother in law didn’t have wifi set up, but she picked up a smart TV this year, so she asked me if I could help her with it. So I picked up a D-Link DIR-615 on sale, brought it with me and set up wi-fi securely (hints: set the SSID to whatever time it happens to be, disable WPS, disable WEP and WPA, and use WPA2 with a long password with some numbers and symbols in it) and once it seemed to be working right, I put her TV and laptop on it. Then, as other relatives trickled in, they asked me for the wireless key. Soon the air was full of Androids and Apples chattering away on wireless.

She said she never realized how often we use our smartphones and tablets. Any time a question came up, someone whipped out a device and looked up the answer.It was nice, and it was a cheap project. Grab a name-brand wireless router on sale, grab a couple of extra CAT5e cables from Monoprice just in case, and you can be a hero for about the cost of dinner for two at any restaurant with sit-down table service. Maybe less.

While you’re ordering stuff from Monoprice, it probably wouldn’t hurt to pick up a small assortment of cheap USB and HDMI cables too, just in case anyone gave an electronic gadget to someone else and didn’t realize gadgets are more likely to come with batteries than with cables these days.

Things I wish everyone knew about home computer security

I’m a security professional by trade, with two certifications. I’m not responsible for defending your computer networks, but I want your networks to be secure. There’s a really simple reason for that. If your computer and your network is secure, then it isn’t attacking mine. Or anyone else’s.

Several fellow subscribers to a train-related interest group that I like got hacked recently, and have been sending out spam messages. They’ve received a lot of advice in the hours since. Some of it has been good, and some not as good. So I tried to think of some things that people could do in about 30 minutes to keep the crooks at bay.

Incidentally, the computer crooks won’t be going away. Computer crime happens because the criminals can make more money doing that than doing something legal. The only way to make it stop is to make it too hard, so that getting a real job becomes more profitable. You won’t solve that problem in 30 minutes, but if we all take that single step down that road, we’ll make the world that much safer. So, with that, let’s roll up our sleeves. Read more

Doc, what security settings are you using on your network?

A reader who will remain anonymous (he can out himself if he wishes) sent me an interesting observation. He was in his doctor’s office last week, and out of curiosity, he ran a wifi scanner on his phone just to see what networks were available and how they were secured.

What he saw wasn’t pretty. Especially considering he was in a building full of doctors, lawyers, and financial advisors. Read more

Securing wi-fi isn’t about price gouging

The so-called wi-fi golden era is over, and apparently being glad about it makes me an absolutist.

But John C. Dvorak is wrong. This isn’t about making people pay for Internet access. It’s pure security. Toilets and drinking fountains are free because the majority of people don’t abuse them. The Internet can’t be wide open and free like a public restroom because when it was totally wide open and free in the 1990s, too many people abused it. Read more

How to make a DMZ with two routers

I’ve alluded in the past to why it’s a good idea to make a DMZ with two routers, but I’ve never gone into depth about how and necessarily why to do it.

If your ISP gave you a combination modem/switch/access point/router and it only supports 100 megabit wired and 54-megabit (802.11g) wireless and you want to upgrade to gigabit wired/150-meg (802.11n) wireless, here’s a great way to make the two devices work together and improve your security.

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How I secured my new wireless router

For the first time ever, I actually have a wireless router that can cover my whole house. I’ve been interested in wireless security for a long time, but haven’t actually had to do much with it because I wasn’t running any wireless networks at home.

I spent a few minutes securing my network after I got it up and running. I talked at rather long length about that in the past, but on a really practical level, here’s what I did in a mere 10 minutes that will make a big difference.

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How to secure your wi-fi router

It’s not enough to know what to look for in a router. I wanted to get some solid advice on wi-fi network security. Who better to give that advice than someone who built an airplane that hacks wi-fi? So I talked to WhiteQueen at http://rabbit-hole.org, the co-builder of a wi-fi hacking airplane that made waves at Defcon.

Hacker stereotypes aside, WhiteQueen was very forthcoming. He’s a white hat, and I found him eager to share what he knows.

“Hypothetically speaking, if you lived next door to me, how long would it take you to get into my wi-fi network?” I asked him.

Surprisingly–at least it surprised me–if you use WPA2 with a strong password, you can make it take years. While I can’t keep him out indefinitely, it’s entirely possible to make it so difficult that anyone not specifically targeting me will just move on to someone else. And you can too.

Why should I care?

Perhaps you heard in the last couple of years about credit card information being leaked out of TJ Maxx and Marshalls store networks. A 29-year-old Cuban-American named Albert Gonzalez admitted to the theft and re-selling of 170 million credit card numbers from 2005-2007. He stole them off poorly secured wireless networks.

The September 2010 issue of Hakin9 magazine (hakin9.org) details the crime, and how it could have been prevented.

WhiteQueen pointed me to page 47, which showed a diagram of Gonzalez’ wardriving setup. All of the equipment is easily obtained, or fabricated using instructions that are readily available.

Passwords

If your password is something like “popcorn,” he can break it in less than 45 minutes. Dictionaries containing a couple million possible weak passwords exist.

So, what’s a good password? He recommends something 14-25 characters long, mixed case, with a couple of numbers and special characters, not substituting numbers and symbols for vowels, l337-style. th!sIz@s3cur3p@ssw0rd! isn’t quite what it claims to be. Use a random password generator, he says. A Google search will turn up web pages that will generate them for you.

You don’t have to type that password all that often, he said, so the pain/security tradeoff isn’t all that high.

WPA2 vs. WPA vs. WEP

You can forget about WEP. There are enough vulnerabilities in WEP that he can break it in minutes. WEP is effectively like the lock on your screen door, only useful for keeping honest people out.

Consider this. There are free tools that run on Android that crack WEP. You can’t install it from Google’s app store–you have to root the phone–but anyone with a little determination can do it. It might take 30 minutes a typical Android phone from 2010 to break a WEP network, but 2011’s phones should be able to do it in about five, which is about how long it takes an Atom netbook, circa 2010, to do the job.

WPA is better, but it also has vulnerabilities. There are automated tools for breaking WPA too. For $17, WPA Cracker will attempt to break a WPA network, and on average, it takes 40 minutes. And it’s not the only option out there.

If you’re serious about keeping someone with his abilities out, use WPA2.

You can increase the security of your WPA or WPA2 network by hibernating or turning off your laptop when you’re not using it. Attacks against WPA require something with an active connection to be using it at the time.

SSID

Setting your SSID to not broadcast is an old security trick, but it doesn’t gain you much anymore.

He said you might as well broadcast your SSID. Wireless networks just work better if you broadcast it, and you don’t slow a hacker down very much by not broadcasting it. You just make the hacker stop and run a tool to look for hidden SSIDs. Not broadcasting the SSID hurts you a lot more than it hurts him, he said.

But don’t include easily identifiable information in your SSID. Keep your last name, house number, and street out of it. Personal information not only helps an attacker identify his target, but it also helps a hacker create a personalized dictionary to run against your network.

Pick something with no connection to you. The more meaningless, the better. The more bland, the better. Don’t make it something that identifies your network as belonging to you, and don’t make it something that makes it look like you’re hiding something interesting.

The best is just a plain old number (other than your house number), or random gibberish.

WhiteQueen said there are mainly two reasons a lowlife might want to get into a network. Either you have data he wants, or he wants to use your network to jump off and do something else. That could be jumping off to hack another network, effectively using you to cover his tracks. Or it could be downloading illegal stuff he doesn’t want to use his own network to download.

Preventing the second case is easy. If your network is harder to hack than your neighbors’, that guy will always pick the guy whose network is wide open, or the guy who never changed his password from the factory default, or the guy who’s still running WEP.

So, the simple advice of using WPA2 with a strong password protects you from that guy.

For extra protection against someone who specifically wants to get into your network to get at your data, he recommends a second router. Or turn off wi-fi completely.

Plug one modem into your router. Assign that router an address space of 10.something. You can set the password to something your laptop-toting houseguests won’t mind typing in, but of course, you want to balance enough strength into it so that passers-by jump on someone else’s network instead of abusing yours. Ten characters, mixed case, with one number and one special character would be reasonable.

Then, plug a second router’s WAN port (not one of its Ethernet ports) into a LAN port in the first router. Assign that router a 192.168 address space. Either turn off its wireless, or turn on WPA2 and assign a nice, strong password to it. Plug your desktop PCs, your NAS, and that kind of stuff into the second router.

For the security paranoid, the two routers should be different. Different revisions of the same model could be OK (such as an early, pre-v5 Linksys WRT54G or WRT54GL based on Linux and a later v5-v8 WRT54G based on VxWorks), but different models or different brands entirely is better. That way, if someone uses a vulnerability in one to get through, he still has to get through a second one to get to your network. Of course, don’t forget to change the default passwords on your routers.

Vulnerabilities in wireless routers do come up from time to time. http://www.cvedetails.com/ has a nice database of vulnerabilities, which you can search by vendor and product. Fortunately, vulnerabilities that crash the router are a lot more common than vulnerabilities that let someone come in and do something.

Fixing them is just a matter of downloading the latest firmware from the vendor and installing it.

Hackin9 adds another step: Lock down the router to allow a limited number of connections. If you have two computers, set the router to only allow two connections. Then hard-code the MAC address of those machines. The procedure to do this varies from router to router.

The moving target

It took about five years for a vulnerability to be found in the original WPA. And brute-force attacks–trying every possible password–are much more practical now than they were in years past. The typical $500 consumer PC of today is a supercomputer compared to anything that was available in 2001.

So far, there are no known vulnerabilities in WPA2, so in 2010 the only way in is to use brute force.

Here’s some good news: A dictionary suitable for cracking 8-character passwords using all 95 of the easily typable characters on the U.S. keyboard would require approximately 11.91 petabytes to store. The largest available hard drive in 2010 is 3 terabytes–an order of magnitude smaller–so it’s safe to say we’re still a few years away from being able to store that kind of information on the desktop.

A dictionary file suitable for hacking 14-character passwords goes consumes a mere 4 brontobytes. What’s a brontobyte? One brontobyte would hold approximately 1,000 copies of the World Wide Web, circa 2010, in its entirety.

This is a bit of an oversimplification, but in 1990, consumer hard drives were measured in megabytes. In 2000, they were measured in gigabytes, and today, in 2010, they’re measured in terabytes. We may be pushing 2020 before we get to petabytes. So it’s more likely that someone will discover a flaw in WPA2 before that’s practical to store. But that, too, will take time.

But don’t feel too secure. A hacker who wants in will throw every dictionary he has at you. And WhiteQueen said hackers tend to collect passwords as they discover them, and add them to their dictionaries. He said humans aren’t very good at being random, so when they find a password one human used, there’s a good chance another human will use it.

The second-best thing you can do is stack the odds in your favor. The best thing you can do is keep your wi-fi turned off.

Things to look for in a wireless router

It’s the time of year that a lot of people buy computer equipment, and wireless networking is one of the things people look for. But what things should be on the shopping list?

I was hoping you’d ask that question.Compatibility with what you already have, if possible. Routers are available that speak 802.11a, 802.11b, and 802.11g, or all three. If you already have some wireless equipment, look for something that can speak its language.

Cordless phone interference. 2.4 GHz cordless phones will interfere with 802.11b and 802.11g. 802.11a works at a different frequency, but it might be cheaper to replace your 2.4 GHz phone with a 900 MHz phone.

Speed. 802.11a and 802.11g operate at 54 Mbps, which is considerably nicer than 802.11b’s 11 Mbps, although both are much faster than current U.S. broadband connections, which tend to top out around 3 Mbps. If you move a lot of files around, you’ll appreciate the 54 Mbps speed. If your primary use of wireless is sharing an Internet connection and a printer or two, 802.11b is probably fast enough, and it’s usually cheaper, with the downside of shorter life expectancy.

802.11g is currently the most popular standard, because it gives 54 Mbps speed and offers compatibility with existing 802.11b equipment. Use this information as you will. If you’re of the security by obscurity mindset, 802.11a is a better choice, as a wardriver is more likely to be driving around with an 802.11b or 802.11g card. If you want to make sure your buddies can hook up when they come over, or you can hook up at your buddies’ places, 802.11g is the better choice.

Brand. Match the brands of router and cards, if at all possible. This makes configuration and security much simpler.

WPA. The encryption used by older standards is relatively weak. You want to enable 128-bit WEP (256-bit WEP is better but still not as good as WPA), change the SSID and disable SSID broadcast, and hard-code your MAC addresses so that only your cards can use your router. This protects you from someone driving around your neighborhood with a laptop and using your Internet connection to send out spam or transfer illicit material that can be traced back to you. Do you want the RIAA suing you because someone used your Internet connection to download 400 gigs’ worth of boy-band MP3s off Kazaa? Worse yet, if that happens, word might get out that you like that stuff.

WPA adds another layer of protection on top of these (which are standard issue by now). Rather than the security key being fixed, it’s dynamically generated from trillions of possibilities. Sufficient CPU power to crack WPA and either monitor your transmissions or use your access point might someday exist, but for now it gives the best protection available, so you should get it and use it. This USRobotics whitepaper on security ought to be a must-read.

Built-in firewall with port forwarding. This is a standard feature on all brand-name units and ought to be on the off brands as well, but it doesn’t hurt to double check. Hardware firewalls are far superior to software firewalls–they don’t annoy you with popups and they can’t be disabled by a malicious process. Port forwarding is necessary for a lot of games, and also if you want to run your own mail or web server.

Hackability. By this I don’t mean the ability of an outsider to get in, I mean your ability to add capability to it. The Linksys WRT54G is based on Linux, so it has a big following with an underground community adding capabilities to it all the time. If you want to take advantage of this, look for a WRT54G or another device with a similar following.