Backtrack Surveillance réseaux - test clés wifi sécurité -clés codage wifi, donc les protocoles WEP et WPA...

A lire :

Ici trés beau tuto : bien détaillé bonnes photos...

Comment fabriquer une antenne Wifi soi même, facilement et surtout pas cher ?
Vous n’avez pas de connaissance dans l’électronique, vous êtes passionnez pour l’informatique, le Wifi et les technologies de communication, ce tutorial est pour vous !
Voila comment se composera le plan :
1) Capter les Réseaux sans fil avec une antenne Pringles
a) Fabrication de l’antenne Pringles
b) Fabrication du câble
c) Carte PCI et connecteur SMA
2) Capter les Réseaux sans fil avec une antenne Ricoré
a) Fabrication de l’antenne Ricoré
3) Comparaison Pringles et Ricoré (NetStrumbler)

Le problème le plus courant est la non compatibilité de votre carte wifi avec Backtrack :(   Si vous prévoyez d'investir, voici une carte wifi usb compatible et tout à fait abordable : la D-LING-G122 .

Pour les personnes voulant pousser la chose plus loin je vous propose la carte wifi usb Alpha AWUS036H qui permet le fixement d'antennes.

Cette carte est considérée par la communauté comme excellente et relativement abordable.  Elle est tellement puissante qu'elle est………bon disons interdite en France ;)

Vous pouvez la trouver sur le Net en fouillant un peu à l'international et vous en sortir pour environ 50€. Son grand avantage en dehors de sa puissance et de pouvoir fixer des antennes.

La première est une antenne omnidirectionnelle 9dbi pour arroser tout autour de l'ordinateur (20€).

La deuxième, la plus intéressante est de type Yagi et permet de capter à plus de 200 mètres (en théorie 1,3 km). Cette dernière coûte 34 € et permet de viser un point comme "un sniper wifi".

Lincomatic's Homebrew WiFi Antenna

Heinz Beans Cantenna

I will not go into the construction details, as they are very well documented on Greg Rehm's site. Finding his online cantenna calculator rather intriguing, I set out to find the mathematical roots to his calculations. The result is my own cantenna calculator program, which I wrote in in C++, based on formulae obtained from the ARRL Antenna Book. It's available on my free software page; the archive contains both a Win32 console-mode EXE and full source code. In addition, Adam Lesser has kindly supplied a binary for OS-X.

Greg Rehm's calculator fixes the operating frequency at Channel 6 (2437MHz), which is the center channel in the USA, giving the best tradeoff if you want to build a general purpose antenna which works across Channels 1-11. On the other hand, my calculator lets you tune your antenna for maximum gain on a specific channel; this is handy if you want to use your antenna set up a permanent point to point link. Let's go through an example using my calculator. The syntax of the program is

cantenna diameter centerchannel

where diameter is in mm. So to make an antenna optimized for Channel 6 using my 3.25" (82.55mm) diameter can, we would invoke it as follows:

D:\>cantenna 82.55 6
Lincomatic Circular Waveguide Calculator V1.1 (Feb 25 2004 23:03:31)

Waveguide diameter: 82.550000 mm (3.250000 in)
Channel: 6 (2437 MHz)

TE11 Cutoff (MHz): 2128.387692
TM01 Cutoff (MHz): 2779.953846
Guide Wavelength (mm): 252.566154 (9.943549 in)
Operating wavelength (mm): 123.017012 (4.843189 in)

1/4 Guide Wavelength (probe to back) (mm): 63.141539 (2.485887 in)
Probe Length (mm): 30.754253 (1.210797 in)

probe pos (Ch1): 66.046774
probe pos (Ch11): 60.564048
probe pos (Ch14): 58.520674
difference between Ch1-Ch11 (mm): 5.482725

So what's the meaning of all this gibberish?  The probe should be 30.8mm (1.21") long, and should be set 63mm (2.5") from the inside of the back lid of the can.  The operating wavelength of 4.8" shows us that we don't have to worry that the sides of the can have ridges, because the their depth is insignificant compared to the wavelength our signal. The Guide Wavelength is the wavelength of our waveguide. The TE11/TM01 Cutoff frequencies give us the approximate upper/lower frequencies of operation for our antenna. Since Channel 1 is centered at 2412MHz and Channel 11 is centered at 2462 MHz, we have a comfortable margin. Now the interesting part is that if you wanted to tune the waveguide for the center frequency of Channel 1, you would use a probe distance of 66.04mm instead, and for Channel 11, you would use 58.52mm. What this means is that there is a whopping 5.48mm difference in the optimal probe distance between Channels 1 and 11, so if you are going to use the antenna on a fixed channel, it's better to enter than channel number instead when running the program.

Experimenting with my calculator program, I've found some interesting information. As the waveguide diameter increases, the difference in optimal position for the driven element between Channels 1-11 drops.  I tried upping the diameter iteratively until the TM01 cutoff frequency started to go too low to do Channel 11. From my studies, it seems that about 92mm is the optimal diameter for the waveguide if you want to try to optimize it for flattest response across Channels 1-11; this is because it minimizes the difference in the probe position between Channels 1-11 -> about 2.63mm, so the SWR curve across the WiFi band is flatter.

Contrary to popular belief on the Internet, a can length of 3/4 the waveguide wavelength is not optimal. The ARRL Antenna book recommends 2-3 waveguide wavelengths instead. I've found that adding more cans indeed increases the gain. A 4-can one is the longest I tried; I didn't write down the gain testing results, but it was considerably better than the 1-can antenna. Adding more cans helps launch the standing waves in the can better. bmoore314 has some excellent info in this Netstumbler.com thread, including info about adding a conical collector to it.  My results from experimenting with a conical collector are documented in the section about my Bazooka Cantenna.

Toothpick Monopole

Comtelco 7.5dBi Patch Antenna Clone

Mobile Mark 5dBi Ommi Clone

• wire: ~1.5mm OD
• ground plane to coils: 34mm (9.5mm of that is under the black plastic bump..wonder what's in there?)
• length of coils: 13mm
• coil ID: 5mm
• coil OD: 7mm
• coil spacing: ~3-3.5mm
• coils to top: 51.5mm+13mm(plastic tip)..wonder how high the wire goes into the tip.

Trevor Marshall's BiQuad

Bazooka Cantenna

Collinear Omni

• Coil wire diameter: 1.5mm
• Coil OD: 6mm
• Coil pitch: 3.5mm center to center
• Tube diameter: 3mm
• Tube length: 56.5mm

Parts List

• (2) 12" long 3/64" diameter brass rod 2x$.59
• (2) 12" long 3/32" diameter brass tube 2x$1.09
• (1) 12" long 11/32" diameter brass tube $1.99
• (1) 2ft long 1/2" diameter PVC pipe $0.10
• (1) 1/2" diameter PVC end cap $0.29
• (1) N-female panel jack $4.50

Construction

1. Hold a piece of 3/64" brass wire against 9/64" drill bit and wind 4 turns, each turn separated by about 3.5mm. Leave about 10mm of straight wire before the turns and 24mm after the turns. Adjust the spacing of the turns with needle nose pliers while the coil is still on the drill bit. Bend the ends neatly with the needle nose pliers. Repeat until you have 4 coils.
2. Cut four 57mm long pieces of 3/32" tubing and one 91.5mm long piece. I used the cutter on a pair of needle-nosed pliers to cut them; this flattened them, which is not bad because the hole in the tubing is actually a loose fit. Next, I used the needle-nosed pliers to squeeze the tubing until the hole opened up large enough to pass the wire into it. Finally, I filed the tubing smooth, which took off about .5mm off its length.
3. Cut a 30mm piece of 11/32" brass tubing. I used a hacksaw and mitre box.
4. Solder the 91.5mm long tube to the center pin of the N-jack. This is the feedline
5. Slip the 30mm tube over the 91.5mm tube, and solder to the N-jack. This tube is the decoupler. The feedline must be supported in order to keep it from shorting on the decoupler; I slid a piece of rubber hose over the feedline.
6. Solder a coil to the feedline, leaving about 3mm of wire between the feedline and the start of the coil.
7. Solder a piece of 3/32" tubing to the other end of the coil, leaving 22mm of straight wire between the last turn and the tubing.
8. Repeat until you get to the top of the antenna.
9. Cut the PVC pipe to the proper length to enclose the antenna and glue on the end cap.
10. Cut pieces of foam to support the antenna inside the PVC pipe - I stuffed the foam into the coils - and carefully slide the antenna into the pipe.
11. Attach the N-jack to the other end of the pipe. You can screw it onto a flat end cap if you can find that style. I chose to just tack the N-jack directly to the pipe with hot glue. Then, I used epoxy over the hot glue for strength and heat resistance.

Performance