How to Crack a Wi-Fi Network's WEP Password with BackTrack

You already know that if you want to lock down your Wi-Fi network, you should opt for WPA encryption because WEP is easy to crack. But did you know how easy? Take a look.

Originally published last year, we wanted to revisit Gina's awesome guide to cracking Wi-Fi WEP passwords for Evil Week. Alternatively, if you're not in a reading mood, check out the video version.

Today we're going to run down, step-by-step, how to crack a Wi-Fi network with WEP security turned on. But first, a word: Knowledge is power, but power doesn't mean you should be a jerk, or do anything illegal. Knowing how to pick a lock doesn't make you a thief. Consider this post educational, or a proof-of-concept intellectual exercise.

Dozens of tutorials on how to crack WEP are already all over the internet using this method. Seriously—Google it. This ain't what you'd call "news." But what is surprising is that someone like me, with minimal networking experience, can get this done with free software and a cheap Wi-Fi adapter. Here's how it goes.

What You'll Need

Unless you're a computer security and networking ninja, chances are you don't have all the tools on hand to get this job done. Here's what you'll need:

• A compatible wireless adapter—This is the biggest requirement. You'll need a wireless adapter that's capable of packet injection, and chances are the one in your computer is not. After consulting with my friendly neighborhood security expert, I purchased an Alfa AWUS050NH USB adapter, pictured here, and it set me back about $50 on Amazon. Update: Don't do what I did. Get the Alfa AWUS036H, not the US050NH, instead. The guy in this video below is using a $12 model he bought on Ebay (and is even selling his router of choice). There are plenty of resources on getting aircrack-compatible adapters out there.
• A BackTrack 3 Live CD. We already took you on a full screenshot tour of how to install and use BackTrack 3, the Linux Live CD that lets you do all sorts of security testing and tasks. Download yourself a copy of the CD and burn it, or load it up in VMware to get started. (I tried the BackTrack 4 pre-release, and it didn't work as well as BT3. Do yourself a favor and stick with BackTrack 3 for now.)
• A nearby WEP-enabled Wi-Fi network. The signal should be strong and ideally people are using it, connecting and disconnecting their devices from it. The more use it gets while you collect the data you need to run your crack, the better your chances of success.
• Patience with the command line. This is an ten-step process that requires typing in long, arcane commands and waiting around for your Wi-Fi card to collect data in order to crack the password. Like the doctor said to the short person, be a little patient.

Crack That WEP

To crack WEP, you'll need to launch Konsole, BackTrack's built-in command line. It's right there on the taskbar in the lower left corner, second button to the right. Now, the commands.

First run the following to get a list of your network interfaces:

airmon-ng

The only one I've got there is labeled ra0. Yours may be different; take note of the label and write it down. From here on in, substitute it in everywhere a command includes (interface).

Now, run the following four commands. See the output that I got for them in the screenshot below.


airmon-ng stop (interface)
ifconfig (interface) down
macchanger --mac 00:11:22:33:44:55 (interface)
airmon-ng start (interface)

If you don't get the same results from these commands as pictured here, most likely your network adapter won't work with this particular crack. If you do, you've successfully "faked" a new MAC address on your network interface, 00:11:22:33:44:55.

Now it's time to pick your network. Run:

airodump-ng (interface)

To see a list of wireless networks around you. When you see the one you want, hit Ctrl+C to stop the list. Highlight the row pertaining to the network of interest, and take note of two things: its BSSID and its channel (in the column labeled CH), as pictured below. Obviously the network you want to crack should have WEP encryption (in the ENC) column, not WPA or anything else.

Like I said, hit Ctrl+C to stop this listing. (I had to do this once or twice to find the network I was looking for.) Once you've got it, highlight the BSSID and copy it to your clipboard for reuse in the upcoming commands.

Now we're going to watch what's going on with that network you chose and capture that information to a file. Run:

airodump-ng -c (channel) -w (file name) --bssid (bssid) (interface)

Where (channel) is your network's channel, and (bssid) is the BSSID you just copied to clipboard. You can use the Shift+Insert key combination to paste it into the command. Enter anything descriptive for (file name). I chose "yoyo," which is the network's name I'm cracking.

You'll get output like what's in the window in the background pictured below. Leave that one be. Open a new Konsole window in the foreground, and enter this command:

aireplay-ng -1 0 -a (bssid) -h 00:11:22:33:44:55 -e (essid) (interface)

Here the ESSID is the access point's SSID name, which in my case is yoyo. What you want to get after this command is the reassuring "Association successful" message with that smiley face.

You're almost there. Now it's time for:

aireplay-ng -3 -b (bssid) -h 00:11:22:33:44:55 (interface)

Here we're creating router traffic to capture more throughput faster to speed up our crack. After a few minutes, that front window will start going crazy with read/write packets. (Also, I was unable to surf the web with the yoyo network on a separate computer while this was going on.) Here's the part where you might have to grab yourself a cup of coffee or take a walk. Basically you want to wait until enough data has been collected to run your crack. Watch the number in the "#Data" column—you want it to go above 10,000. (Pictured below it's only at 854.)

Depending on the power of your network (mine is inexplicably low at -32 in that screenshot, even though the yoyo AP was in the same room as my adapter), this process could take some time. Wait until that #Data goes over 10k, though—because the crack won't work if it doesn't. In fact, you may need more than 10k, though that seems to be a working threshold for many.

Once you've collected enough data, it's the moment of truth. Launch a third Konsole window and run the following to crack that data you've collected:

aircrack-ng -b (bssid) (file name-01.cap)

Here the filename should be whatever you entered above for (file name). You can browse to your Home directory to see it; it's the one with .cap as the extension.

If you didn't get enough data, aircrack will fail and tell you to try again with more. If it succeeds, it will look like this:

The WEP key appears next to "KEY FOUND." Drop the colons and enter it to log onto the network.

Problems Along the Way

With this article I set out to prove that cracking WEP is a relatively "easy" process for someone determined and willing to get the hardware and software going. I still think that's true, but unlike the guy in the video below, I had several difficulties along the way. In fact, you'll notice that the last screenshot up there doesn't look like the others—it's because it's not mine. Even though the AP which I was cracking was my own and in the same room as my Alfa, the power reading on the signal was always around -30, and so the data collection was very slow, and BackTrack would consistently crash before it was complete. After about half a dozen attempts (and trying BackTrack on both my Mac and PC, as a live CD and a virtual machine), I still haven't captured enough data for aircrack to decrypt the key.

So while this process is easy in theory, your mileage may vary depending on your hardware, proximity to the AP point, and the way the planets are aligned. Oh yeah, and if you're on deadline—Murphy's Law almost guarantees it won't work if you're on deadline.

---

To see the video version of these exact instructions, check out this dude's YouTube video.

Got any experience with the WEP cracking courtesy of BackTrack? What do you have to say about it? Give it up in the comments.

Gina Trapani, Lifehacker's founding editor, is tired of typing commands that start with "air." Her weekly feature, Smarterware, appears every Wednesday on Lifehacker. Subscribe to the Smarterware tag feed to get new installments in your newsreader.

Contact information for this author is not available.

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more about #wep

Crack a Wi-Fi Network's WEP Password with BackTrack, the Fancy Video Version

The Definitive Guide to Finding Free Wi-Fi

read more: #wifi, #wep, #stepbystep, #security, #homenetwork, #linux, #linuxlivecd, #livecd, #vmware, #clips, #howto, #screenshottour, #feature, #top, #smarterware, #downloads, #commandline, #evilweek

Question Tutorial 1

1. Briefly explain traditional role of quantity surveyor in commercial building projects

Answer:The quantity surveyor is a major contributor to the success of all types of project in all sectors of the economy including the industry infrastructure , healthcare , education , public buildings , retail and commerical construction , residential construction , and leisure projects.
The role of quantity surveyor including cost estimating , cost advice , cost planning , property development advice , advice on tendering procedures and contractual arrangement , prepare tender document , prepare contract documents , valuation of work in progress , financial control over contracts , final account in respect of the contract and etc

Future service of quantity surveyor

• Offering advice on property taxation
• Providing post-occupancy advise , facilities management services and life cycle costing advice
• Assisting clients in locating and accessing additional and alternative sources of funds
• Advising on the maintenance costs of specific buildings
• Life cycle cost analysis /planning
• Construction planning
• Arbitration/ Mediation
• Expert witness/ appraisal Insurance valuations
• Risk Management
• Project/construction management
• Value management
• Quanlity Management
• Facilities/asset management
• Premises audit (energy etc.)
• Due diligence reports
• Cost benefit analysis
• Information management
• ETC.
  

ROle of quantity surveyor ?

• Prepare tender documents:

-Doing taking-off , preparing bills of quantities and other tender documents ( form of tender , conditions of tender , preliminaries , preambles to all trades , specification etc) for tendering purposes.

-Manage the tender process - Organize the calling of tenders , clarify and evaluate tenders (for example examining tenders and priced bulls of quantities and reporting findings ) prepare tender report and involve in tender interview.

-Negotiating rates with contractors on negotiated contracts and dealing with cost reimbursement contracts , design and build , management and other form of contracts.

• Prepare contract documents:

-Prepare contract documents ( contents are same as tender documents but there are additional documents of correspondence and form of contract ) which will sign by the successful tenderer and the client ; distributed to all project parties ( successful contractor , client , quantity surveyor , architect , c&s engineer and M&E engineer).

• Valuation of work in progress

-Interim valuation of works in progress on site for purposes of interim payments.

-Valuing work in progress and making recommendations as to payments to be made to the contractor , including advising on the financial effect of variations.

• Financial control over contracts

-Preparing financial statement to monitor project cost during the construction stage.

-Performing variation control and assessment of contractor's claims during construction stage.

• Final account in respect of the contract

-Preparing final account on completion of the contract works

-The quantity surveyor's duty is essentially one of cost control. They measure and value work in progress , determine the value of variations ordered by the architect or engineer and ensure that a fair and equitable settlement of the cost of the project is reached in accordance with the contract conditions . In conjunction with the architect and other consultants , the quantity surveyor will ensure that the dinancal provisions of the contract are properly interpreted and applied .

• However , the role of quantity surveyor is distinct between QS working in:

-Consulatant Firms

-COntractor firms

-Developer firms

-Architect firms

• Generally , the role of quantity surveyor working in contravtor firm including :

-A contractor's QS is responsible for the performance of operations that mirror those of the owner;s QS . For ecample the measurement and pricing of construction work.

-The role of a contractor's QS will extend further than the day to day running of building projects and will cover such other areas as sub-contract formation , forecasting of costs and values of the project , cash flow forecasts and the collation of the operation and maintenance manuals of the project ( O&M manuals ).

Role of Quantity Surveying

• Cost estimating

-Preparation of preliminary cost estimate and measurement of constructon works prior to tender in the very early stages of the formulation of a building project.

• Cost advice

-Giving cost advice and information during all stages of the development of a project to assure full awareness of financial implications of the project.

-Giving advice on alternative materials and components and types of construction and the financial aspects of contracts and assiting with feasibility studies.

• Cost Planning

-Cost planning and value analysis during the design stage of a project to ensure that client obtains value for money where the costs are distributed in most realistic way throughtout the various sections or elements of the building not olny with regard to the capital cost but also in respect of the running and maintenance cost of a project and that the tender figure is kept within the client's budget.

-Cost planning enables decisions on various design alternatives to be made with actual costs being constantly monitored against original budgets.

• Property development advice

-A building should meet the functional dimensional and technological requirement for which it was designed , should be aesthetically pleasing and meet the cost limits of the client's budget.

-A quantity surveyor is able to provide pre-design feasibility studies involving technical and/or economic investigations thereby enabling a client to decide whether , and in what form , to proceed.

• Advice on tendering procedures and contractual arrangement

-The choice of an appropriate form of contract for any given project will depend on the nature of the project , the circumstances under which the work is to be carried out and the particular needs of the client.

-Quantity Surveyor , in collaboration with architects are able to advise the client on the most advantages procurement method available , including : contracts incorporating bulls of quantity , provisional bills of quantities and schedules of rates.

Who is quantity surveyor ?

• A quantity surveyor (QS) is a professional working within the construction industry .
• Generally , the role of the QS is to manage and control contracts and costs within construction projects.
• The quantity surveyor is a major contributor to the success of all types of projects in all sectors of the economy including industry , infrastructure , healthcare , education , public buildings , retail and commercial construction , residential construction , and leisure projects

History of Quantity Suerveying

Measurement Lexture 1

• The quantity surveyor emerged in England at the begining og the nineteenth century , although the firm of Henry Cooper and Sons of Reading was established as early as 1785.
• Prior to the first recorded usage of the term "quantity surveyor" in 1859 , the term "measurer" , "custom surveyor " or "surveyor " were used .
• In those early days , the quantity surveyor acted for the master tradesmen , measuring the work after completion and frequently submitting partisan Final Accounts to the building owner .

objective of measurement

• This unit aims to expose students to the function and importance of tender documenttation , methods of doing the taking-off and measurement of substructure works : all in accordance with the Standard Method of Measurement of Building Works (SMM2)

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