Home > Information Security, Tips and Tricks > Crack A Wi-Fi Network’s WPA Password With Reaver

Crack A Wi-Fi Network’s WPA Password With Reaver

image-reaver

Reaver exploits a security hole in wireless routers and can crack most routers’ current passwords with relative ease

Your Wi-Fi network is your convenient wireless gateway to the internet, and since you’re not keen on sharing your connection with any old hooligan who happens to be walking past your home, you secure your network with a password, right? Knowing, as you might, how easy it is to crack a WEP password, you probably secure your network using the more bulletproof WPA security protocol.

Here’s the bad news: A new, free, open-source tool called Reaver exploits a security hole in wireless routers and can crack most routers’ current passwords with relative ease. Here’s how to crack a WPA or WPA2 password, step by step, with Reaver — and how to protect your network against Reaver attacks.

In the first section of this post, I’ll walk through the steps required to crack a WPA password using Reaver. After that, I’ll explain how Reaver works, and what you can do to protect your network against Reaver attacks.

What You’ll Need

You don’t have to be a networking wizard to use Reaver, the command-line tool that does the heavy lifting, and if you’ve got a blank DVD, a computer with compatible Wi-Fi, and a few hours on your hands, you’ve got basically all you’ll need. There are a number of ways you could set up Reaver, but here are the specific requirements for this guide:

  • The BackTrack 5 Live DVD. BackTrack is a bootable Linux distribution that’s filled to the brim with network testing tools, and while it’s not strictly required to use Reaver, it’s the easiest approach for most users. Download the Live DVD from BackTrack’s download page and burn it to a DVD. You can alternately download a virtual machine image if you’re using VMWare, but if you don’t know what VMWare is, just stick with the Live DVD. As of this writing, that means you should select BackTrack 5 R1 from the Release drop-down, select Gnome, 32- or 64-bit depending on your CPU (if you don’t know which you have, 32 is a safe bet), ISO for image, and then download the ISO.
  • A computer with Wi-Fi and a DVD drive. BackTrack will work with the wireless card on most laptops, so chances are your laptop will work fine. However, BackTrack doesn’t have a full compatibility list, so no guarantees. You’ll also need a DVD drive, since that’s how you’ll boot into BackTrack. I used a six-year-old MacBook Pro.
  • A nearby WPA-secured Wi-Fi network. Technically, it will need to be a network using WPA security with the WPS feature enabled. I’ll explain in more detail in the “How Reaver Works” section how WPS creates the security hole that makes WPA cracking possible.
  • A little patience. This is a 4-step process, and while it’s not terribly difficult to crack a WPA password with Reaver, it’s a brute-force attack, which means your computer will be testing a number of different combinations of cracks on your router before it finds the right one. When I tested it, Reaver took roughly 2.5 hours to successfully crack my password. The Reaver home page suggests it can take anywhere from four to 10 hours. Your mileage may vary.

Let’s Get Cracking

 

How Reaver Works

Now that you’ve seen how to use Reaver, let’s take a quick overview of how Reaver works. The tool takes advantage of a vulnerability in something called Wi-Fi Protected Setup, or WPS. It’s a feature that exists on many routers, intended to provide an easy setup process, and it’s tied to a PIN that’s hard-coded into the device. Reaver exploits a flaw in these PINs; the result is that, with enough time, it can reveal your WPA or WPA2 password.

Read more details about the vulnerability at Sean Gallagher’s excellent post on Ars Technica.

How To Protect Yourself Against Reaver Attacks

Since the vulnerability lies in the implementation of WPS, your network should be safe if you can simply turn off WPS (or, even better, if your router doesn’t support it in the first place). Unfortunately, as Gallagher points out as Ars, even with WPS manually turned off through his router’s settings, Reaver was still able to crack his password.

In a phone conversation, Craig Heffner said that the inability to shut this vulnerability down is widespread. He and others have found it to occur with every Linksys and Cisco Valet wireless access point they’ve tested. “On all of the Linksys routers, you cannot manually disable WPS,” he said. While the Web interface has a radio button that allegedly turns off WPS configuration, “it’s still on and still vulnerable.

So that’s kind of a bummer. You may still want to try disabling WPS on your router if you can, and test it against Reaver to see if it helps.

You could also set up MAC address filtering on your router (which only allows specifically whitelisted devices to connect to your network), but a sufficiently savvy hacker could detect the MAC address of a whitelisted device and use MAC address spoofing to imitate that computer.

Double bummer. So what will work?

I have the open-source router firmware DD-WRT installed on my router and I was unable to use Reaver to crack its password. As it turns out, DD-WRT does not support WPS, so there’s yet another reason to love the free router-booster. If that’s got you interested in DD-WRT, check their supported devices list to see if your router’s supported. It’s a good security upgrade, and DD-WRT can also do cool things like monitor your internet usageset up a network hard drive, act as a whole-house ad blockerboost the range of your Wi-Fi network, and more. It essentially turns your $US60 router into a $US600 router.

 

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