Computer Software

Although a wireless transmitter is limited in its range, wireless extension points can be installed to boost its signal and make the range of the network much larger. These wireless extension points are commonly known as repeaters.

Several companies have started to manufacture wireless repeaters, despite the fact that these devices are not part of the wireless standard. Wireless repeaters are designed to resolve certain problems with wireless coverage. The further away you are from where the wireless signal originates, the weaker the signal becomes. Eventually, you can’t receive the signal at all, regardless of what equipment you have. The problem is sometimes addressed by running wires out as far as the network coverage is desired, and then have it ‘break out’ into wireless every now and then using a wireless access point. This is generally more trouble that it is worth, since the idea behind a wireless network is to avoid installing wires! Wireless repeaters resolve the problem in a much better way.

Wireless repeaters work as a relay, taking existing wireless signals and making them stronger. This makes the range of a signal bigger each time. If the repeaters are placed correctly, you can move computers a considerable distance from the wired portion of the network, the router or access point, for example, without failure. The single requirement of this arrangement is that the extension points must overlap; a repeater can’t repeat signals that it doesn’t receive. Since wireless networking signals are essentially radio signals, repeaters take all the radio signals they receive on a specific frequency and use their power to amplify the signals and rebroadcast them. The signal is not degraded in this process, so it can be repeated as many time as required.

Theoretically, wireless repeaters could be placed in a line for several miles, extending the network out that far, and because these extension points don’t need complicated computer technology to operate, they are much cheaper than routers or access points. Some companies combine repeaters and direction antennas to link to LANs that are several miles apart. This is a cheaper method than worrying about connecting over the Internet or installing their own underground lines. In the future, repeater technology could create wireless networks that cover entire cities.

As a consumer, you are currently limited to getting your repeater from large manufacturing firms such as Linksys and D-Link. These companies call their repeaters by different names, including Linksys’ Range Expander and D-Link’s Range Extender. There are several issues to consider when buying a wireless extension point. The most important is to make sure that it is compatible with the equipment you have. Because there is no standard for wireless extension points, you’re better off staying with the same company that makes the rest of your equipment or at least investigate whether any new equipment will work with your system. You should also find out whether an extension point has any Ethernet ports. While it isn’t necessary that this is included, it is useful if you want to connect the extension to a wired network. This issue arises basically if you want to connect two LANs in a wireless manner.

The Answer To The Media Access Control Question
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Over the past few weeks I have received quite a few e-mails about Ethernet cards, both wired and wireless, and more specifically, about Media Access Control (MAC) addresses. I think the main reason I’ve received so many questions about Ethernet cards and MAC addresses is people trying to secure their home wireless networks and their desire to use MAC address filtering. This type of filtering in wireless networks can be configured to allow or deny specific computers to use or attach to the wireless network, based on the MAC address.

My first thought was to write an article just about MAC addresses and wireless Ethernet. After thinking about it I decided to expand on this and go over some specific information about Ethernet cards and communication.

Different Ways Of Finding Your MAC Address And More
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There are several ways of finding your Ethernet and communications protocol information. Many Ethernet card manufacturer’s have proprietary software that can reveal this information but they work differently depending on the manufacturer. So we will use the Windows 2000 and XP “ipconfig” utility since this is available in the majority of Windows Operating Systems.

First, go to “start” -> “run” and type “cmd” without the quotes. Then hit the enter key. At the command line type “ipconfig /all”, again without the quotes. Actually, just typing ipconfig without the /all will work but will only provide you with abbreviated information regarding your network cards. An example of what you might see by typing the “ipconfig /all” command is below with each item commented in green lettering:

Fault Tolerant And Highly Availability Computer Systems
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There are several ways of finding your Ethernet and communications protocol information. Many Ethernet card manufacturer’s have proprietary software that can reveal this information but they work differently depending on the manufacturer. So we will use the Windows 2000 and XP “ipconfig” utility since this is available in the majority of Windows Operating Systems.

First, go to “start” -> “run” and type “cmd” without the quotes. Then hit the enter key. At the command line type “ipconfig /all”, again without the quotes. Actually, just typing ipconfig without the /all will work but will only provide you with abbreviated information regarding your network cards. An example of what you might see by typing the “ipconfig /all” command is below:

OutPut Of The “Ipconfig /All” Command
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Windows IP Configuration

Host Name . . . . . . . . . . . . : Home Computer
This is the name of your computer, typically defined during the windows installation. However, it can be changed after installation.

Primary Dns Suffix . . . . . . . : domain.com
If your computer participates in a network such as a Microsoft Windows domain this item may contain the name of the domain.

Node Type . . . . . . . . . . . . : Unknown
The Node Type may say Unknown, or peer-to-peer, or in some cases “hybrid”. It is a setting that has to do with the Windows Internet Naming Services used in certain types of Windows domain networks.

IP Routing Enabled. . . . . . . . : No
This setting determines if Windows XP or 2000 will function as an IP router. If you have two or more network cards you can setup your system to act as a router, forwarding communications requests from one network to another. Windows 2000 can be configured to do this in a pretty straight forward fashion; Windows XP will need a registry modification.

WINS Proxy Enabled. . . . . . . . : No
WINS Proxy is another setting that is related to the “Node Type” we discussed earlier. It is normally not a required setting in a home or small office network, or newer types of Microsoft Windows domains.

Ethernet adapter Wireless Network Connection 2:
If you have multiple Ethernet (network) cards in your systems, as I do in this laptop, you will have multiple listings. This one happens to be the second Ethernet card, an internal wireless Ethernet card.

Description . . . . . . . . . . . : Broadcom 802.11b/g WLAN
This is the description of the Ethernet card, usually the Name / Manufacturer and type of Ethernet card. In this case, it is a Broadcom wireless Ethernet card built into my laptop.

Physical Address. . . . . . . . . : 00-90-4B-F1-6E-4A
And here we have the MAC address. The MAC address is a 48 bit hexadecimal code and is suppose to be a totally unique address. It is 48 bits because each number or letter in hexadecimal represents 8 bits. Hexadecimal numbers range from 0,1,2,3,4,5,6,7,8,9,A,B,C,D,E, F. There are 6 alpha-numeric codes hence 6*8=48(bits). The first 3 codes identify the manufacturer of the card and the remaining codes are used to create a unique number. Theoretically there should never be a card with same MAC address on a local network. However, there are a few exceptions. There are software tools that allow you to change this code. In fact, this is a step some hackers take to attack other systems on a local network. I say local network because MAC addresses are not routable between network segments. By spoofing this address, you can impersonate another machine on the local network. Traffic that was bound for the intended target can be redirected to the hacker’s machine. This is the address you would also use to populate a MAC address, or physical address table when setting up your wireless access point to support MAC address filtering.

DHCP Enabled. . . . . . . . . . . : Yes
DHCP, or the Dynamic Host Control Protocol, if enabled means your computers IP address is being provided by a DHCP server on you network. The DHCP server could be your wireless access point, cable/dsl router, cable modem, or a server on your network. Also, if a DHCP server is not enabled on your network, your computers Operating System will auto generate a random IP address within a certain predefined range. This means you could network a group of systems together without having to manually assign the IP settings.

IP Address. . . . . . . . . . . . : 192.168.0.117
This parameter provides you with your current IP address. The address listed above is what is called a “private” address. There are certain classes of IP addresses that have been set aside for private use. This means for your internal, local, or private network at home or office. These addresses are not, or should not, be routable on the Internet. The Internet routes what are called “valid” IP addresses. Your cable/dsl router or cable modem has a valid IP address assigned to its “external” network interface. The external interface may be your phone line or cable TV cable.

Subnet Mask . . . . . . . . . . . : 255.255.255.0
The Subnet Mask is a special number, or in some sense, filter, that breaks down your IP address, in this case private IP address, into certain groups. IP addresses and Subnet Masks can be a complicated matter and would take an entire article to go over.

Default Gateway . . . . . . . . . : 192.168.0.254
The default gateway, the IP addresses listed above, is the IP address of the device that will route your request, such as when you try to browse a website, to the Internet. It is a bit more complicated than that though as gateways or routers can route traffic to various different networks, even other private networks. At your home or small office, this gateway most likely is your cable/dsl modem or router.

DHCP Server . . . . . . . . . . . : 192.168.0.49
The DHCP server, remember we talked a little about this above, is the device that assigns your computer an IP address and other information. DHCP servers can assign all kinds of information such as; Default Gateway, Domain Name Servers (DNS), IP address, Subnet Mask, Time Server, and much more.

DNS Servers . . . . . . . . . . . : 192.168.0.49, 64.105.197.58
DNS Servers are internal or external servers that resolve Fully Qualified Domain Names (FQDN), such as www.defendingthenet.com , to IP addresses. This is done because computers don’t actually transmit your requests using the domain name, they use the IP address assigned to the FQDN. For most home or small office users, the primary DNS server is the IP address of your cable/dsl router. Your cable/dsl router than queries an external DNS server on the Internet to perform the actual resolution of the FQDN to IP address. The address 192.168.0.49 is an internal private device on my network whereas the 64.105.197.58 is an external public Internet DNS server and is present just in case my router has trouble performing the DNS resolution tasks.

Lease Obtained. . . . . . . . . . : Sunday, March 19, 2006 6:38:16 PM
This information tells you when your computer received its IP address and other information from a DHCP server. You will notice it says “Lease Obtained”, that is because most DHCP servers only lease the IP address to you from a pool of available address. For instance, your pool may be 192.168.1.1 through 192.168.1.50. So your DHCP server has 50 IP addresses to choose from when assigning your computer its IP address.

Lease Expires . . . . . . . . . . : Wednesday, March 29, 2006 9:38:16 PM
When the IP address, assigned by the DHCP server, lease expires it will attempt to lease you the same or another IP address. This function can typically be changed on the DHCP server. For instance, on some fully functional DHCP servers, you can configure the Lease to never expire, or to expire within 1 day and so on.

Why Are MAC Addresses So Important And How Do They Work
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To jump back to MAC address for just a bit. You may think that IP addresses are the most important thing when it comes to network communication. The reality is, MAC addresses are very important because without them computers would not be able to communicate over Ethernet networks. When a computer wants to speak with another computer on a local network, it will make a broadcast request, or ask a question, of who owns a particular IP address. For instance, your computer may say “Who is 192.168.0.254”. Using the information above, my default gateway is 192.168.0.254 and will answer “I am “00-90-4B-F1-6E-4A” 192.168.0.254”. It sends back its MAC address. That MAC address then goes into what is called a Address Resolution Protocol (ARP) table on your computer. You can see this information by going to the command prompt like you did above and typing “arp –a”. You will get information like the following:

Internet Address Physical Address Type
192.168.0.49 00-12-17-5c-a2-27 dynamic
192.168.0.109 00-12-17-5c-a2-27 dynamic
192.168.0.112 00-0c-76-93-94-b2 dynamic
192.168.0.254 00-0e-2e-2e-15-61 dynamic

How A Hacker Can Use MAC Addresses In An Attack
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You will notice the IP addresses and to the right of them the MAC addresses. Without this information, without the MAC address, you would not be reading this article right now. MAC addresses are not routable like IP addresses. They work on your local or private network. However, devices on the Internet perform the same tasks. Routers and switches maintain a list of their peer devices MAC address just like your computers and devices on your home or office network. I mentioned above that MAC addresses can be changed in order to redirect requests. For instance, if I were on your office network and you had an internal web server that took personal information as input, I could tell your computer to go to my laptop for the web site by broadcasting my MAC address tied to the real web servers IP address. I would do this when you computer asked “Who is the “Real Web Server””. I could setup a fake web server that looks just like the real thing, and start collecting information the real web server would normally collect. You can see how dangerous this can be.

Conclusion
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There are several other easy ways you can find your MAC address but they can be a little confusing if you have more than one internal network card. Most external USB, or PCMCIA wired and wireless Ethernet cards have their MAC address printed on them. In cases where the wired or wireless network card are inside your computer, such as in laptops, the MAC address is sometimes printed on the bottom of the laptop. Even Desktop systems cards that are inserted in PCI slots have the MAC address printed on the Ethernet card.

You may reprint or publish this article free of charge as long as the bylines are included.

Original URL (The Web version of the article)
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http://www.defendingthenet.com/NewsLetters/FindingYourMACAddressOnWiredAndWirelessNetworkCards.htm

About The Author
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Darren Miller is an Information Security Consultant with over seventeen years experience. He has written many technology & security articles, some of which have been published in nationally circulated magazines & periodicals. If you would like to contact Darren you can e-mail him at Darren.Miller@defendingthenet.com. If you would like to know more about computer security please visit us at http://www.defendingthenet.com.

To the information security professional wireless networking may be thought of as a four letter word to be avoided at all costs. Regardless of the security implication wireless networking can provide cost efficiency, and because of that wireless technologies are here to stay. While many in the profession believe that wireless networks can be easily compromised, this class will show how the appropriate wireless architecture with the proper security controls can make your wireless network as secure as any other remote access point into your network.

In this three day, wireless security workshop, we will examine the cutting edge of wireless technologies. The purpose of the course is to give you a full understanding of what wireless (802.11) networks are, how they work, how people find them and exploit them, and how they can be secured. This hands-on course is based on real world examples, solutions, and deployments. In this course we will actually set up and use wireless networks, determine the tools to uncover wireless networks, and also look at how to defeat the attempts to secure wireless networks.

Course Completion
Upon the completion of our CISM course, students will have:

Constructed a wireless network architecture
Install and configure 802.1x authentication using Microsoft Windows IAS and Server 2000
Install a wireless access point
Distinguish between 802.11x standards
Defeat Wired Equivalent Privacy
Key Take Aways:

An understanding of wireless networks
A CD of common tools and documentation
An ability to search the internet for updates and more information on wireless networks
Detail of Course Content The following topics will be covered:

Wireless History
Radio Frequency (RF) Fundamentals
WLAN Infrastructure
802.11 Network Architecture
802.1X Authentication
Extensible Authentication Protocol (EAP)/(LEAP)/(PEAP)
Detection Platforms
WLAN Discovery Tools
Kismet
Wireless Sniffers
Conventional Detection
Antennas
Exploiting WLANs
Securing WLANs
Other Wireless Options
Legal Issues including GLBA and ISO-17799
Future
Resources

http://www.acquisitiondata.com/wireless_security.asp

Wireless networks use radio waves instead of wires to transmit data between computers. Here’s how:

The Binary Code: 1s and 0s

It’s well known that computers transmit information digitally, using binary code: ones and zeros. This translates well to radio waves, since those 1s and 0s can be represented by different kinds of beeps. These beeps are so fast that they’re outside the hearing range of humans.

Morse Code: Dots And Dashes

It works like Morse code, which is a way to transmit the alphabet over radio waves using dots (short beeps) and dashes (long beeps). Morse code was used manually for years via telegraph to get information from 1 place to another very quickly. More importantly for this example, though, it is a binary system, just as a computer system is.

Wireless networking, then, can be thought of as a Morse code for computers. You plug in a combined radio receiver and transmitter, and the computer is able to send out its equivalent of dots and dashes (bits, in computer-speak) to get your data from here to there.

Wavelengths And Frequencies

You might wonder how the computer can send and receive data at high speed without becoming garbled nonsense. The key to wireless networking is how it gets around this problem.

First, wireless transmissions are sent at very high frequencies, which allows more data to be sent per second. Most wireless connections use a frequency of 2.4 gigahertz (2.4 billion cycles per second) — a frequency similar to mobile phones and microwave ovens. However, this high frequency produces a wavelength that is very short, which is why wireless networking is effective only over short distances.

Wireless networks also use a technique called “frequency hopping.” They use dozens of frequencies, and constantly switch among them. This makes wireless networks more immune to interference from other radio signals than if they transmitted on a single frequency.

Internet Access Points

The final step for a wireless network is to provide internet access for every computer on the network. This is done by a special piece of wireless equipment called an access point. An access point is more expensive than a wireless card for 1 computer, because it contains radios capable of communicating with around 100 computers, sharing internet access among them. Dedicated access points are necessary only for larger networks. With only a few computers, it is possible to use 1 of them as the access point, or to use a wireless router.

Industry Standards

Wireless equipment from different manufacturers can work together to handle these complex communications because there are standards which guide the production of all wireless devices. These standards are technically called the 802.11. Because of industry compliance with these standards, wireless networking is both easy to use and affordable today.

Wireless Is Simple To Use

If all this talk of frequencies has you worried — relax. Wireless networking hardware and software handle all of this automatically, without need for user intervention. Wireless networking, for all its complicated ability, is far simpler to use than you might expect.

Wireless networks work using radio waves instead of wires to transmit data between computers. That’s the simple version. If you’re curious to know what’s going on in more detail, then it’s all explained in this article.

Ones and Zeros.

I’m sure you know that computers transmit data digitally, using binary: ones and zeros. This is a way of communicating that translates very well to radio waves, since the computer can transmit ones and zeros as different kinds of beep. These beeps are so fast that they’re outside a human’s hearing range — radio waves that you can’t hear are, in fact, all around you all the time. That doesn’t stop a computer from using them, though.

Morse Code.

The way it works is a lot like Morse code. You probably already know that Morse code is a way of representing the alphabet so that it can be transmitted over radio using a dot (short beep) and a dash (long dash). It was used manually for years, and became a great way of getting information from one place to another with the invention of the telegraph. More importantly for this example, though, it is a binary system, just like a computer’s ones and zeros.

You might think of wireless networking, then, as being like Morse code for computers. You plug a combined radio receiver and transmitter in, and the computer is able to send out its equivalent of dots and dashes (bits, in computer-speak) to get your data from one place to another.

All About Frequencies.

You might wonder, though, how the computer could possibly transmit enough bits to send and receive data at the speed it does. After all, there must be a limit on how much can be sent in a second before it just becomes useless nonsense, right? Well, yes, but the key to wireless networking is that it gets around this problem.

First of all, wireless transmissions are sent at very high frequencies, meaning that more data can be sent per second. Most wireless connections use a frequency of 2.4 gigahertz (2.4 billion cycles per second) — a similar frequency to mobile phones and microwave ovens. As you might know, though, a frequency this high means that the wavelength must be very short, which is why wireless networking only works over a limited area.

In addition, wireless networks make use of a technique known as ‘frequency hopping’. They use dozens of frequencies in the range they are given, and constantly switch between them. This makes wireless networks more immune to interference from other radio signals than they would be if they only transmitted on one frequency.

Access Points.

The final step is when it comes to all the computers on a network sharing Internet access. This is done using a special piece of wireless equipment called an access point. Access points are more expensive than wireless cards for one computer, as they contain radios that are capable of talking to around 100 computers at the same time, and sharing out access to the Internet between them. Dedicated access points are only really essential for larger networks, though — if you only have a few computers, it is possible to use one of them as the access point, or you could just get a wireless router.

They Understand Each Other.

That’s all well and good, then, but how does wireless equipment made by entirely different companies manage to work together when this is all so complicated? Well, the answer is that there are standards that all wireless devices follow. These standards are technically called the 802.11 standards, and are set by the IEEE (Institute of Electrical and Electronics Engineers). It is thanks to people sticking to their standards that wireless networking is so easy and cheap to use today.

You Don’t Need to Worry.

If all this talk of frequencies has you a little worried, you don’t need to be — wireless networking hardware and software handles all of this automatically, without you needing to do a thing. Don’t think that you’re going to have to tell one wireless device what frequency another is using, because it’s just not going to happen, alright? Wireless networking, for all its complicated workings, is really far more simple to use than you’d ever expect.