In most solar systems, solar panels are placed on the roof. An ideal site will have no shade on the panels, especially during the prime sunlight hours of 9 a.m. to 3 p.m.; a south-facing installation will usually provide the optimum potential for your system, but other orientations may provide sufficient production. Trees or other factors that cause shading during the day will cause significant decreases to power production. The importance of shading and efficiency cannot be overstated. In a solar panel, if even just one of its 36 cells is shaded, power production will be reduced by more than half. Experienced installation contractors such as NW Wind & Solar use a device called a Solar Pathfinder to carefully identify potential areas of shading prior to installation.
Not every roof has the correct orientation or angle of inclination to take advantage of the sun's energy. Some systems are designed with pivoting panels that track the sun in its journey across the sky. Non-tracking PV systems should be inclined at an angle equal to the site’s latitude to absorb the maximum amount of energy year-round. Alternate orientations and/or inclinations may be used to optimize energy production for particular times of day or for specific seasons of the year.
Solar panels
Solar panels, also known as modules, contain photovoltaic cells made from silicon that transform incoming sunlight into electricity rather than heat. (”Photovoltaic” means electricity from light — photo = light, voltaic = electricity.)
Solar photovoltaic cells consist of a positive and a negative film of silicon placed under a thin slice of glass. As the photons of the sunlight beat down upon these cells, they knock the electrons off the silicon. The negatively-charged free electrons are preferentially attracted to one side of the silicon cell, which creates an electric voltage that can be collected and channeled. This current is gathered by wiring the individual solar panels together in series to form a solar photovoltaic array. Depending on the size of the installation, multiple strings of solar photovoltaic array cables terminate in one electrical box, called a fused array combiner. Contained within the combiner box are fuses designed to protect the individual module cables, as well as the connections that deliver power to the inverter. The electricity produced at this stage is DC (direct current) and must be converted to AC (alternating current) suitable for use in your home or business.
Inverter
The inverter is typically located in an accessible location, as close as practical to the modules. In a residential application, the inverter is often mounted to the exterior sidewall of the home near the electrical main or sub panels. Since inverters make a slight noise, this should be taken into consideration when selecting the location.
The inverter turns the DC electricity generated by the solar panels into 120-volt AC that can be put to immediate use by connecting the inverter directly to a dedicated circuit breaker in the electrical panel.
The inverter, electricity production meter, and electricity net meter are connected so that power produced by your solar electric system will first be consumed by the electrical loads currently in operation. The balance of power produced by your solar electric system passes through your electrical panel and out onto the electric grid. Whenever you are producing more electricity from your solar electric system than you are immediately consuming, your electric utility meter will turn backwards!
Net meter
In a solar electric system that is also tied to the utility grid, the DC power from the solar array is converted into 120/240 volt AC power and fed directly into the utility power distribution system of the building. The power is “net metered,” which means it reduces demand for power from the utility when the solar array is generating electricity – thus lowering the utility bill. These grid-tied systems automatically shut off if utility power goes offline, protecting workers from power being back fed into the grid during an outage. These types of solar-powered electric systems are known as “on grid” or “battery-less” and make up approximately 98% of the solar power systems being installed today.
Other benefits of solar
By lowering a building’s utility bills, these systems not only pay for themselves over time, they help reduce air pollution caused by utility companies. For example, solar power systems help increase something called “peak load generating capacity,” thereby saving the utility from turning on expensive and polluting supplemental systems during periods of peak demand. The more local-generating solar electric power systems that are installed in a given utility's service area, the less capacity the utility needs to build, thus saving everyone from funding costly additional power generating sources. Contributing clean, green power from your own solar electric system helps create jobs and is a great way to mitigate the pollution and other problems produced by electricity derived from fossil fuel. Solar-powered electrical generating systems help you reduce your impact on the environment and save money at the same time!
We'll start with a few nifty tips that can make your desktop more
interesting, make it easier to get around and increase your computer's
power efficiency.
Use hidden international wallpapers and themes
When you first install Windows 7, it asks for your language, time and
currency. Based on your responses, it installs a set of wallpapers and
themes. If you choose English (United States) for your time and currency
format, for example, the available desktop backgrounds and themes will
include a United States section with scenery from locations such as
Maine, the Southwest and so on.
Hidden, though, are background scenery and themes from other
English-speaking countries -- Australia, Canada, Great Britain and South
Africa. Normally, you can't access those backgrounds or themes, but
there is a simple way you can install and use them:
1. In the search box in the Start menu, type C:\Windows\Globalization\MCT and press Enter. (Note: If Windows 7 is installed in a drive other than C:, use that letter instead.)
2. Windows Explorer will launch and show you a list of subfolders under C:\Windows\Globalization\MCT:
MCT-AU, MCT-CA, MCT-GB, MCT-US, and MCT-ZA. Each subfolder has
wallpapers for a specific country: AU for Australia, CA for Canada, GB
for Great Britain, US for the United States, and ZA for South Africa.
A South Africa theme, ready to use.
Click to view larger image.
For any of the countries whose wallpaper and themes you want to use, go into its Theme folder, for example, C:\Windows\Globalization\MCT\MCT-ZA\Theme. Double-click the theme you see there (for example ZA).
3. That will install a shortcut to the theme and wallpapers in the Personalization section of Control Panel.
You can now use them as you would any other theme or background, by
right-clicking the desktop, choosing Personalize, and choosing a
background or theme. They will be listed in their own section.
Shake your desktop free of clutter
If you frequently run multiple programs simultaneously, your desktop can
get extremely cluttered. This can get annoying if you're working on one
program and want to minimize all the other windows -- in previous
versions of Windows you had to minimize them individually.
With Windows 7's "shake" feature, though, you can minimize every window
except the one in which you're currently working -- in a single step.
Click and hold the title bar of the window you want to keep on the
desktop; while still holding the title bar, shake it quickly back and
forth until all of the other windows minimize to the taskbar. Then let
go. To make them return, shake the title bar again.
You can accomplish the same thing by pressing the Window key-Home key
combination -- although doing that is not nearly as much fun.
Get a power efficiency report
Have a laptop and want to get more battery life out of it? Windows 7
includes a hidden built-in tool that will examine your laptop's energy
use and make recommendations on how to improve it. To use it:
1. Run a command prompt as an administrator. To do this, type cmd in the search box, and when the cmd icon appears, right-click it and choose "Run as administrator."
2. At the command line, type in the following:
powercfg -energy -output \<i>Folder</i>\Energy_Report.html
where \Folder represents the folder where you want the report to be placed.
A laptop's power efficiency report.
Click to view larger image.
3. For about a minute, Windows 7 will examine the behavior of your
laptop. It will then analyze it and create a report in HTML format in
the folder you specified. Double-click the file, and you'll get a report
-- follow its recommendations for ways to improve power performance.
Modify UAC
The User Account Control security feature was one of the most reviled
additions to Windows Vista, with good reason -- its constant warning
messages asking for permission to continue many operations drove users
around the bend.
UAC has been significantly improved in Windows 7 so that it's not as
intrusive as in Vista, but you can still tweak it if you like.
Here's how to turn UAC on or off, and make it less or more intrusive than the default:
1. Go to the Control Panel --> User Accounts and Family Safety.
2. Click User Accounts, then click Change User Account Control settings.
3. From the screen that appears, use the slider to select the level of
protection you want. Here are the four levels and what they mean:
Modifying UAC. Click to view larger image. Always notify me. Think of this as UAC Classic. It works like
Vista's UAC: When you make changes to your system, when software is
installed or when a program tries to make a change to your system, an
annoying prompt appears.
Default -- Notify me only when programs try to make changes to my computer.
This is, obviously, the default; make a change yourself and UAC leaves
you alone. When a program makes a change, a prompt appears and your
desktop goes dark, just like it does in Vista. Otherwise, UAC sits there
silently.
Notify me only when programs try to make changes to my computer (do not dim my desktop).
This setting is identical to the default setting, with one difference:
It won't dim your desktop so that you only see the UAC prompt asking you
to take action. This presents a slightly elevated security risk over
the default setting, because theoretically a program could allow a
malicious program to interfere with the UAC prompt.
Never notify me when: In this one, UAC is completely turned off. This is, of course, an insecure option and not recommended for most users.
After you make the selection, click OK. Depending on the selection you
made, you may need to restart your system for it to take effect.
Start Menu tips
Many people overlook the Start Menu, rarely using it except as a jumping
off point to run an application or get to the Control Panel. But
there's actually plenty you can do with it.
Search the Internet from the Start Menu
Note: This tip relies on the Group Policy Editor, which isn't
available in some versions of Windows 7. Thus, this tip will not work if
you have the Home Premium, Starter, or Home Basic editions of Windows
7.
The Start Menu's search box is a convenient way to search through your
PC -- but you can also have it do double-duty and perform Internet
searches as well. To enable this feature:
1. In the Start Menu search box, type GPEDIT.MSC and press Enter to run the Group Policy Editor.
2. Go to User Configuration --> Administrative Templates --> Start Menu and Taskbar.
Enabling Internet search from the Start Menu.
Click to view larger image.
3. Double-click "Add Search Internet link to Start Menu," and from the
screen that appears, select Enabled. Then click OK and close the Group
Policy Editor.
4. From now on, when you type a search term in the Search box on the
Start Menu, a "Search the Internet" link will appear. Click the link to
launch the search in your default browser with your default search
engine.
Customize the Shut down button
The default action of the Start Menu's Shut down button is to turn off
your PC. If you want to use the button for another action, such as
restarting your PC, you click the arrow to the right of the Shut down
button and select an action from the drop-down menu.
What if you rarely shut your PC down completely but frequently restart
it? You can change the Shut down button's default action to be Restart
-- or Switch user, Log off, Lock, Sleep or Hibernate.
To change your default, right-click the Start button and select
Properties. On the Start Menu tab, click the "Power button action"
drop-down menu and select which action you want to be the default. Then
click OK, and OK again.
Add a Videos link to the Start Menu
The Windows 7 Start Menu includes links to your Pictures and Music
folders, but not to your Videos folder. If you watch a lot of videos and
want a link to them on your Start Menu, here's what you can do:
Displaying the Videos folder on the Start Menu.
Click to view larger image.
1. Right-click the Start button and select Properties.
2. On the screen that appears, go to the Start Menu tab and click Customize.
3. In the dialog box that appears, scroll to the bottom, look for the
Videos section, select "Display as a link," and click OK and then OK
again.
If you'd prefer that Videos display as a menu, with links to files and submenus, instead select "Display as a menu."
Windows Explorer tips
Windows Explorer is the heart and soul of the Windows interface, and overall it works quite well. But you can make it better.
Use check boxes to select multiple files
In order to select multiple files for an operation such as copying,
moving or deleting in Windows Explorer, you generally use the keyboard
and the mouse, Ctrl-clicking every file you want to select.
But if you're mouse-centric, there's a way to select multiple files in
Windows 7 using only your mouse, via check boxes. To do it:
Selecting multiple files using your mouse and check boxes.
Click to view larger image.
1. In Windows Explorer, click Organize, and then select "Folder and search options."
2. Click the View tab.
3. In Advanced Settings, scroll down and check the box next to "Use check boxes to select items." Click OK.
4. From now on, when you hover your mouse over a file in Windows
Explorer, a check box will appear next to it; click it to select the
file. Once a file is selected, the checked box remains next to it; if
you uncheck it, the box will disappear when you move your mouse away.
Open a command prompt at any folder
Command prompt fans will welcome this tip. With it, when you're in
Windows Explorer, you can open a command prompt to any folder. This tip
does exactly what the Windows XP PowerToy "Open Command Window Here" does.
To use it, hold down the Shift key and right-click a folder, then choose
"Open command window here" from the context menu that appears. (Note
that this tip doesn't work in the Documents folder.)
Protect the privacy of your Explorer searches
Note: This tip relies on the Group Policy Editor, which isn't
available in some versions of Windows 7. Thus, this tip will not work if
you have the Home Premium, Starter, or Home Basic editions of Windows
7.
When you search through your PC from Windows Explorer, you can see the
most recent searches that have been performed. If you share a PC and
don't want others to see what you've searched for, you can turn off the
recent searches feature:
1. In the Start menu's Search box, type GPEDIT.MSC and press Enter to launch the Group Policy Editor.
Select "Enabled" to protect search privacy.
Click to view larger image.
2. Go to User Configuration --> Administrative Templates --> Windows Components --> Windows Explorer.
3. Double-click "Turn off display of recent search entries in the
Windows Explorer search box" and select Enabled from the screen that
appears. Then click OK. The recent searches feature will now be turned
off.
Set a new Windows Explorer launch folder
When you run Windows Explorer, it always opens to the Libraries folder.
That's fine if you use Microsoft's default file organization, which
designates Libraries as the overall container for your folders.
But what if you don't? You might prefer to have Windows Explorer open to
Computer or any other folder you choose. Here's how to do it:
Changing the default Explorer location.
Click to view larger image.
1. Right-click the Windows Explorer icon on the taskbar (it's the one
that looks like a folder), and then right-click the Windows Explorer
icon from the context menu that appears and select Properties. The
Windows Explorer Properties dialog box appears.
2. You'll have to edit the Target field on the Shortcut tab of this
dialog box in order to change the default location at which Explorer
opens.
If you want Explorer to open to a specific folder, simply enter the name of the folder, substituting your folder name for Folder, below, like this:
%windir%\explorer.exe c:\<i>Folder</i>
So to open Explorer to the folder named Budget, you would type this in the Target field:
%windir%\explorer.exe c:\Budget
If you want Explorer to open to special, pre-set locations, such as
Computer, you'll need to enter special syntax in the Target field.
Following is a list of three common locations and the syntax to use,
followed by the syntax for the Libraries folder in case you ever want to
revert to the default.
3. After you've changed the Target field, click OK. Next time you launch
Windows Explorer, it will open to the new location you've designated.
Show all your drives in Windows Explorer
Depending on your system settings, when you go to Computer in Windows
Explorer, you may be in for a shock -- you may not see all your drives
such as memory card readers if those drives are empty. If this
disconcerts you, there's a simple way for you to see them even if
there's nothing there:
Having Explorer show empty drives.
Click to view larger image.
1. Launch Windows Explorer and press the Alt button to reveal the top menu.
2. Select Tools --> Folder Options and click the View tab.
3. Under "Advanced settings," uncheck the box next to "Hide empty drives
in the Computer folder." Click OK. The drives will now always be
visible.
Build your own Internet Search Connector
Windows 7 has a very useful new feature called a Search Connector that
lets you search through a Web site from right inside Windows Explorer.
With it, you type in a search term and select the Search Connector for
the site you want to search; Explorer searches the Web site without
having to open Internet Explorer, and the results appear inside Windows
Explorer. Click any of the results to head there using your default Web
browser.
Normally, you'll need to get each Search Connector from the Web site
through which you want to search, and very few Connectors are available.
Sites normally need to adhere to OpenSearch standards in order for their Connectors to work.
Adding a new Search Connector.
However, there's a work-around that will let you easily build your own
Search Connector for any site, using Windows Live Search as a kind of
go-between. Don't worry, you don't need to know any code to write a
Connector. Just follow these steps:
1. Copy the following text and paste it into Notepad. The text you'll need to change is in bold, all-caps text:
<?xml version="1.0" encoding="UTF-8"?> <OpenSearchDescription
xmlns="http://a9.com/-/spec/opensearch/1.1/"
xmlns:ms-ose="http://schemas.microsoft.com/opensearchext/2009/">
Microsoft's Patch Tuesday for August contains critical patches for Windows, Internet Explorer and Read Now
<ShortName>NAME YOUR SEARCH</ShortName> <Description>DESCRIPTION OF SEARCH</Description> <Url type="application/rss+xml" template="http://api.bing.com/rss.aspx?source=web&query={searchTerms} site:SITENAME.COM&web.count=50"/> <Url type="text/html" template="http://www.bing.com/search?q={searchTerms}+site:SITENAME.COM"/> </OpenSearchDescription>
2. In place of NAME YOUR SEARCH, type in the name of the search as you want it to appear. In our case, we're going to build a Search Connector for Computerworld, so we'll just type in Computerworld.
3. In place of DESCRIPTION OF SEARCH, type in a longer description of the search. In our instance, it will be Search through Computerworld.
4. In the two SITENAME.COM entries, enter the Web site's domain. Don't use the http:// or www -- just the domain name. In our instance it will be computerworld.com.
5. To the right of "count=", type in the number or results you want to appear. In our instance, we'll keep it at 50.
6. In our example, here's what the code should look like (no bold necessary):
<?xml version="1.0" encoding="UTF-8"?>
<OpenSearchDescription
xmlns="http://a9.com/-/spec/opensearch/1.1/"
xmlns:ms-ose="http://schemas.microsoft.com/opensearchext/2009/"> <ShortName>Computerworld</ShortName> <Description>Search through Computerworld</Description> <Url type="application/rss+xml" template="http://api.bing.com/rss.aspx?source=web&query={searchTerms} site:computerworld.com&web.count=50"/> <Url type="text/html" template="http://www.bing.com/search?q={searchTerms}+site:computerworld.com"/> </OpenSearchDescription>
7. Save the file in Notepad, choose UTF-8 from the Encoding drop-down
box near the bottom of the Save As screen, and give it an .osdx
extension. In our instance, we'll call the file Computerworld.osdx.
8. In Windows Explorer, right-click the .osdx file and select Create Search Connector. The Search Connector will be created.
9. You can now use the Search Connector. To get to it, in Windows Explorer go to YourName --> Searches --> Connector, where YourName is your account name, and Connector is the name of the Connector.
One of the most significant changes to the Windows 7 interface is its new taskbar,
which acts more like the Mac OS X dock than the Windows taskbar of old.
Here are a few quick tips for using the new taskbar and tweaks for
taking charge of it.
Speed up the display of thumbnails on the taskbar
One of the nicest things about the taskbar is that when you hover your
mouse over the icons in it, you can see thumbnail previews of all open
windows for each of those applications.
The taskbar in thumbnail view.
Click to view larger image.
When you do so, there is a slight delay before the thumbnail appears.
But you can make the thumbnails display more quickly by using a Registry
hack.
Important: Always create a Restore Point before editing the Windows
Registry. If you don't know how to create a Restore Point or find your
way around the Windows Registry, see "The tweaker's guide to the Windows Registry."
1. Launch the Registry Editor by typing regedit in the Search box and pressing Enter.
2. Go to HKEY_CURRENT_USER\Control Panel\Mouse.
3. Double-click MouseHoverTime. The default value you'll
see is 400 -- which means 400 milliseconds. Type in a new, smaller value
-- 150 is a good bet. Then click OK and exit the Registry Editor.
You'll have to log off or restart your computer for the change to take
effect.
Rearrange taskbar icons
It's easy to rearrange the icons across the bottom of the screen --
simply drag an icon to where you want it to live. You can also add icons
to the taskbar by dragging them from an application, and delete the
icons by highlighting them and pressing the Delete key.
Take control of the taskbar notification area
The notification area, at the far right of the taskbar, shows system
messages and alerts, and displays the icons of programs and services
that typically run in the background, such as Windows 7's wireless
service. But what determines when, how and which icons show up there
seems one of Windows' great mysteries.
There's a simple way to find out, and better yet, to customize it.
Customizing the taskbar notification area.
Click to view larger image.
1. Right-click the taskbar, select Properties, and from the dialog box in the notification area section, click Customize.
2. For each application, select from the drop-down box whether you want
the icon and notifications to always be displayed, to never be displayed
or to have an icon appear only when there's a notification of some
kind. Click OK when you're done.
You can also customize the system icons and services that appear there,
including the clock, volume, network, power and Action Center icons. At
the bottom of the same screen, click "Turn system icons on or off," and
from the screen that appears, choose whether to turn on or off the icon
and notifications. Click OK twice when you're done.
See taskbar thumbnails without a mouse
If you're a fan of using the keyboard rather than your mouse whenever
possible, you can move your cursor from icon to icon in the taskbar
without a mouse -- and still see thumbnail previews.
Press Windows key-T, and you'll move the focus to the leftmost icon on
the taskbar. Then, while still pressing the Windows key, press T again
to change the focus to the next icon to the right. You can keep doing
this as long as you like.
Launch taskbar apps without a mouse
Likewise, you can launch any program on the taskbar without the mouse.
Press the Windows key and the number that corresponds to the position of
the application on the taskbar -- for example, Windows key-1 to launch
the left-most application on the taskbar, Windows key-2 to launch the
second left-most application and so on.
Run multiple copies of applications from the taskbar
The Windows 7 taskbar serves a dual purpose, which can get confusing at
times. It's used to launch programs, and also to switch between programs
that are running. So you launch a program by clicking its icon, and
also switch to that program after it's running by clicking its icon.
But what if you want to launch a second instance of the program? Once
the program is running, it seems there's no way to launch a second
instance, because when you click its icon, you only switch to the
running instance.
There's a simple fix: If a program is already running and you want to
launch a second instance from the taskbar, hold down the Shift key and
click the icon. A second instance will launch. You can keep launching
new instances this way.
Get back the Quick Launch bar
Windows 7's new taskbar functions as a program launcher as well as task
switcher. As a result, the old Quick Launch bar, the area on the left
side of the taskbar that contained shortcuts for frequently used
programs, has been banished. However, if you really miss the little
applet, you can add it back. Here's how to do it:
1. Right-click the taskbar and choose Toolbars --> New Toolbar.
2 . You'll be asked to select a folder for where the new toolbar should
live. In the Folder text box at the bottom of the dialog box, enter this
text: %userprofile%\AppData\Roaming\Microsoft\Internet Explorer\Quick Launch
After you do that, click Select Folder. A link for the Quick Launch bar
will be added to the taskbar. It will be on the right of the taskbar,
just to the left of the Notification area.
The Quick Launch bar docked on the right. Click to view larger image.
It's not particularly useful docked all the way to the right with no
application icons showing, so we're going to have to do a bit of work on
it to make it useful. Right-click the taskbar and, in the pop-up menu,
remove the check next to "Lock the taskbar." Now right-click Quick
Launch and remove the checks next to Show Text and Show Title.
Once you've done that, drag the vertical triple dotted line next to the
Quick Launch bar to the left until you expose its icons. To prevent
further changes, right-click the taskbar and check Lock the taskbar. You
can now use the Quick Launch bar as you could in Windows XP and Vista,
including adding icons to it and deleting them.
Try to kill the Autorun file by following these steps:
Download the file AutorunExterminator
Extract it --> Double-click on "AutorunExterminator" --> Plug in your external hard drive.
This will remove the autorun.inf files from your external hard drive.
Run the following command. Here I assume your external hard drive is G:
attrib -h -r -s /s /d g:\*.*
You can copy the above command and then right-click in the Command Prompt to paste it.
(Or do "Start" --> "Run" and type Ctrl+V.)
A
wireless local area network (WLAN) is the linking of 2 or more
computers with Network Interface Cards (NICs) through a technology based
on radio waves. All devices that can connect to a wireless network are
known as stations. Stations can be access points (APs), or clients.
Access
points are base stations for the wireless network. They receive and
transmit information for the clients to communicate with. The set of all
stations that communicate with each other is referred to as the Basic
Service Set (BSS). Every BSS has an Identification known as a BSSID,
also known as the MAC address, which is a unique identifier that is
associated with every NIC. For any client to join a WLAN, it should
know the SSID of the WLAN; therefore, the access points typically
broadcast their SSID to let the clients know that an AP is in range.
Data streams, known as packets, are sent between the Access Point, and
it’s clients. You need no physical access to the network or its wires to
pick up these packets, just the right tools. It is with the
transmission of these packets that pose the largest security threat to
any wireless network.
Wireless Encryption
The majority of home and small business networks are encrypted using the two most popular methods:
WEP & WPA
WEP
– Wired Equivalent Privacy – comes in 3 different key lengths: 64, 128,
and 256 bits, known as WEP 64, WEP 128, and WEP 256 respectively. WEP
provides a casual level of security but is more compatible with older
devices; therefore, it is still used quite extensively. Each WEP key
contains a 24 bit Initialization Vector (IV), and a user-defined or
automatically generated key; for instance, WEP 128 is a combination of
the 24 bit IV and a user entered 26 digit hex key. ((26*4)+24=128)
WEP also comes in WEP2 and WEP+, which are not as common and still as vulnerable as the standard WEP encryption.
WPA
– WiFi Protected Access – comes in WPA and WPA2, and was created to
resolve several issues found in WEP. Both provide you with good
security; however, they are not compatible with older devices and
therefore not used as widely. WPA was designed to distribute different
keys to each client; however, it is still widely used in a (not as
secure) pre-shared key (PSK) mode, in which every client has the same
passphrase.
To fully
utilize WPA, a user would need an 802.1x authentication server, which
small businesses and typical home users simply cannot afford. WPA
utilizes a 48 bit Initialization Vector (IV), twice the size of WEP,
which combined with other WEP fixes, allows substantially greater
security over WEP.
Packets and IVs
It’s
all in the packets. The bottom line is – while you may be able to
employ several security features on your WLAN – anything you broadcast
over the air can be intercepted, and could be used to compromise the
security on your network. If that frightens you, start stringing wires
throughout your home.
Every
encrypted packet contains a 24 or 48 bit IV, depending on the type of
encryption used. Since the pre-shared key is static and could be
easily obtained, the purpose of the IV is to encrypt each packet with a
different key. For example, to avoid a duplicate encryption key in every
packet sent, the IV is constantly changing. The IV must be known to
the client that received the encrypted packet in order to decrypt it;
therefore, it is sent in plaintext.
The
problem with this method is that the Initialization Vectors are not
always the same. In theory, if every IV was different, it would be
nearly impossible to obtain the network key; this is not the case. WEP
comes with a 24 bit IV; therefore, giving the encryption 16 million
unique values that can be used. This may sound like a large number, but
when it comes to busy network traffic, it’s not.
Every
IV is not different; and this is where the issues arise. Network
hackers know that all the keys used to encrypt packets are related by a
known IV (since the user entered WEP part of the key is rarely changed);
therefore, the only change in the key is 24 bits. Since the IV is
randomly chosen, there is a 50% probability that the same IV will repeat
after just 5,000 packets; this is known as a collision.
If
a hacker knows the content of one packet, he can use the collision to
view the contents of the other packet. If enough packets are collected
with IV matches, your network’s security can be compromised.
The crack
Two
of the most popular programs used for actually cracking the WEP key are
Airsnort and Aircrack. Airsnort can be used with the .dump files that
Kismet provides; and Aircrack can be used with the .cap files that
Airodump provides.
Airsnort
can be used on it’s own without any other software capturing packets;
although, it has been reported to be extremely unstable in this state,
and you should probably not chance loosing all your captured data. A
better method would be to let Airsnort recover the encryption key from
your Kismet .dump file. Kismet and Airsnort can run simultaneously.
For
this demonstration, we’ll be using Aircrack. You can use Airodump to
capture the packets, and Aircrack to crack the encryption key at the
same time.
With Airodump running, open a new command window and type: aircrack -f 3 -n 64 -q 3 george.cap
The -f switch
followed by a number is the fudgefactor; which is a variable that the
program uses to define how thoroughly it scans the .cap file. A
larger number will give you a better chance of finding the key, but will
usually take longer. The default is 2.
The -n switch
followed by 64 represents that you are trying to crack a WEP 64 key. I
knew because it was a setup; In the real world there is no way to
determine what WEP key length a target access point is using. You may
have to try both 64 and 128.
The -q 3 switch
was used to display the progress of the software. It can be left out
altogether to provide a faster crack; although, if you’ve obtained
enough unique IVs, you should not be waiting more than a couple minutes.
A -m switch
can be used, followed by a MAC address, to filter a
specific AP’s usable packets; this would come in handy if you were
collecting packets from multiple APs in Airodump.
Aircrack recovered my WEP 64 key within 1 minute using 76,000 unique IVs; the whole process took around 34 minutes.
The
same experiment was repeated with WEP 128 and it took about 43 minutes.
The reason it was not substantially longer is because I simply let
Airplay replay more packets. Sometimes you can get lucky and capture an
ARP Request packet within a few minutes; otherwise, it could take a
couple hours.
Netcut: Disconnect
any wifi devices from network. Support windows OS . The driver and
Install package has been upgrade. tested working under windows 7 both 32
bit and 64 bit OS. Its change MAC address on any adapter, including
wireless. Details at How to change MAC. Also support Clone MAC address
from any PC that NetCut monitored. Whereas Wifikill use for
Android applications to disable internet connections for a device on
same network. Disconnect wifi connection and get full network on your
device.
To access your ADSL router or modem, connect your computer to the router and then open up your web browser(e.g. Internet Explorer) and type in the default IP-address. If this doesn't take you to the Login screen then the IP-address may have been changed. Please enter the new IP-address instead.
D-Link ADSL routers and modems have a factory default IP-address of 192.168.1.1 with a subnet of 255.255.255.0
To access your ADSL router or modem, connect your computer to the
router and then open up your web browser(e.g. Internet Explorer) and
type in the default IP-address.
If this doesn't take you to the Login screen then the IP-address may
have been changed. Please enter the new IP-address instead. If you can't
remember the changed IP-address and don't know how to find that
information you can always reset the router so it goes back to factory
default settings.
