The most common application of NFC (Near Field Communication) is to make credit card payments using an NFC enabled smart phone and NFC enabled Point of Sale terminal. One just needs to tap the smart phone over the PoS equipment or hover the phone very near to it, to make the payment securely.

Near Field Communication (NFC) operates in the 13.56 MHz frequency band and currently supports data rates of 106 Kbps to 424 Kbps. Since NFC is a very short range communication network and the messages exchanged between two NFC enabled devices are encrypted, the protocol is relatively secure. But NFC has its own security threats and needs to address certain security concerns arising due to user mis-handling – Smart phones getting stolen, for example.

There are passive NFC tags that can store a small amount of information securely. One can attach them to any device, like how an RFID tag is attached. A passive NFC tag does not need a power source and it can communicate with an Active NFC device using the power generated by the magnetic field of the Active NFC device in its range. Active NFC devices need dedicated power source to communicate with each other. NFC technology is compatible with RFID, by the way.

NFC enables faster and more intuitive interaction between two devices and it is complimentary to Bluetooth, Zigbee, RFID and Wi-Fi wireless networks.

Applications of NFC – Near Field Communication:

• Used to make credit card payments securely – Customers can tap their NFC enabled smart phones over NFC enabled Point of Sale equipments to make a payment. This way, the transaction is also secure because the counter clerk does not get to see the credit card number.
• Passive, low cost NFC Tags can be attached to any object like retail products/ museum exhibits and the customer can hover their smart phone over them to get more details (like price, description, etc) about them.
• Two NFC enabled devices can share photos, videos, music, applications or any other data between them.
• Business cards or money can be transfered between two NFC enabled devices (like smart phones) directly.
• NFC enabled smart phones (for example) can be used to instantly buy bus tickets / train tickets when a passenger gets to the station.
• NFC chips can be embedded into a small credit card type (form-factor) cards that can be used as an ID Card or to make instant transactions over the counter.
• NFC enabled devices can be used to pay to vending machines in fairs/ unmanned areas.
• NFC can be used to instantly configure two devices to connect using long range wireless networks like bluetooth or Wi-FI, without requiring the complex set-up procedure normally involved to initiate them.
• Parking lot ticket payments.
• It can secure credit card payments by storing and making payments using a series of one-time use credit card numbers.
• Smart phones can download instant receipt for transactions made through NFC. These receipts can be later sent to the employer for reimbursements.
• NFC can be used for checking into location aware services like Foursquare to get deals, product promotions, suggestions, etc based on one’s location.
• It can be used to make payments securely, where ever a Point of Sale equipment is required. For example, one can buy movie tickets, tickets for sports/ events, etc.

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Well, we all know what it took to upgrade our ‘b/g’ network to ‘n’ network. New Access Points, New Controller (with a higher throughput capacity), New Backbone Cabling / POE Gigabit Switches, New client adapters (or) New laptops, and what not!  Basically, the up-gradation demanded replacing most of the Network components.

Many companies and organizations have not even fully upgraded to the 802.11n network which provides a (shared) throughput capacity of 450 Mbps/ 600 Mbps, depending on a lot of factors. In this backdrop, do we need another high-speed wireless standard?

New technologies do take some time to mature and get fully implemented. By the time the new wireless network is ready, bandwidth hungry applications should be ready to take advantage of them as well!

IEEE 802.11ac Wireless Standard:

802.11ac would operate on Sub-6 Ghz frequencies. It is expected to operate primarily in the 5 Ghz spectrum and perhaps in the 2.4 Ghz spectrum as well. These two frequency ranges are already common with the older standards and they belong to unlicensed frequency spectrum, almost throughout the world.

The 802.11ac Wireless standard is expected to give a throughput of around 1 Gbps. The actual throughput may vary from 293 Mbps to 3.5 Gbps depending on a number of factors like Number of MIMO Spatial streams used, Modulation technique, short guard interval, etc.

802.11ac is expected to have backward compatibility with 802.11n/a, as these technologies can operate in the 5Ghz spectrum. Further, 802.11ac is expected to support higher channel bandwidth of 80 MHz / 160 MHz (Optional) to give higher throughput, in addition to supporting 20 Mhz, 40 Mhz, etc. used by the earlier standards.

802.11ac is also expected to support multiple bandwidth operation (few clients operating with a higher bandwidth, few with a lower bandwidth simultaneously) within a frequency band, in order to fully support legacy clients on the network. So, one can migrate to this standard in a phased manner while still retaining many of the 802.11n network components.

802.11ac might support a technology called MU-MIMO (Multi User MIMO) where multiple STA’s can transmit and receive independent data streams simultaneously.

This standard is expected to be available by the end of 2012, but one can expect the Wi-Fi alliance certified, IEEE draft compliant products available earlier.

IEEE 802.11ad Wireless Standard:

802.11ad would operate in the 60 Ghz spectrum, which is also a part of the unlicensed frequency band in most of the countries. One of the advantages of  60 GHz frequency is the fact that it has more available spectrum than the 2.4 Ghz and 5 Ghz frequency bands.

The 802.11ad Wireless standard is expected to give a throughput of around 7 Gbps but higher bandwidth can be realized at relatively shorter ranges.

The channel bandwidth for each channel in 802.11ad might be as much as 50 times more that what was available with 802.11n. This enables higher speeds and throughput.

Don’t be surprised if Tri-band radios (Operating in 60 Ghz, 5 Ghz & 2.4 Ghz) become available for interoperability with earlier standards and multi-band operation. But these details are not yet confirmed.

Upgrading to 802.11ad wireless standard might not only require changing wireless access points / client wireless adapters, but it might also require new wireless controllers.

There is another upcoming wireless standard called WiGig developed by an industry consortium. This standard is similar to 802.11ad as it operates in the 60 Ghz spectrum and they have even contributed to 802.11ad standard. So, 802.11ad and WiGig are expected to be inter-operable.

Its quite early to comment on these upcoming wireless standards and this article intends to throw some light on their technicalities, based on information available at present. But when these standards are actually released, they are expected to incorporate the latest advances in technology available by then.

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What is Zigbee/ 802.15.4 Network?

Zigbee is a Wireless Networking standard like Wi-Fi. Zigbee even operates in the same unlicensed frequency spectrum of 2.4 Ghz like Wi-Fi, but the similarity ends there. Zigbee devices form self configuring, self healing wireless networks that use low cost devices (radios, clients) to achieve a limited throughput (250 Kbps). The low bandwidth might surprise you initially, but that is sufficient for many applications.

Zigbee is the name of the alliance formed by independent companies that have some interest in manufacturing inter-operable wireless sensors and radios that can work with Zigbee standard and 802.15.4 is the IEEE Standard for the same. While IEEE 802.15.4 defines the physical and MAC layers, Zigbee itself defines the network and application layers of this wireless network. It means that all Zigbee devices will work with each other, irrespective of the manufacturer.

Features of Zigbee/ 802.15.4 Network:

• Throughput: 250 Kbps at 2.4 Ghz with 16 Channels / 40 Kbps at 915 Mhz with 10 Channels
• Transmission distance: 100 meters (Can be lesser in indoor and higher in outdoor conditions)
• Frequency: Uses unlicensed bands, can work anywhere in the world without requiring special permissions
• System resources required: 4-32 Kb
• Battery life: Around 1000 Days, Low power design
• Scalability: Highly scalable network that can accommodate up to 64,000 nodes using a single coordinator
• Relationship with Wi-Fi: Zigbee Networks can interfere with Wi-Fi if both are operating in 2.4 Ghz and they are not designed to inter-operate natively
• Cost: Zigbee Routers and Sensors cost very less (compared to Wi-Fi) and hence are more suitable for bulk deployment
• Network Topology: Uses Mesh Topology, Star Topology and Peer-to-Peer Topology, and can work in any one of them
• Power: Battery powered, no need for running cables across the premises

Applications of Zigbee/ 802.15.4 Network:

Some applications suitable for Zigbee / 802.15.4 Wireless network include : Industrial automation, Energy automation, Access Control, Heart rate monitor, Home security, Environmental control, Lighting control, Meter reading, HVAC / Heating control, etc.

Components of Zigbee/ 802.15.4 Network:

Coordinator: There is one coordinator (generally) in a Zigbee network that stores the network configuration information, security keys and all other important information about the network. This is the control unit of the whole Zigbee network. But in large networks, multiple Coordinators can be linked together. The end points/ sensors can connect directly with the coordinator, if required.

Router: Since the range of the Coordinator is limited, Routers are used to extend the Zigbee networks.  They have a range of 100 meters each, and they are kept within the range of other nearby routers so that they can form a mesh network. They connect the end users with the coordinator.

End point / Sensor/ Client: This is the small sensor that can be connected with any device that needs to transmit / receive control messages through the wireless network. They can be connected to the router / coordinator to be able to communicate with other devices.

Advantages of the Mesh Network used in Zigbee Networks:

The routers that are used to extend the Zigbee networks can connect with each other (within a certain range) using a Mesh Network. In fact, each router is connected to at least two more routers in a properly planned Zigbee network. Since these devices are battery powered (low power) devices, they don’t need any cables to connect back to the coordinator.

Each router not only transmits and receives messages intended for the end clients/ end points connected to it but also relays the messages of the other routers connected to it.

The Mesh architecture not only avoids backbone cabling, but also provides a good degree of fault tolerance. Even if one access point is down, the messages could be routed through others. The Zigbee network is designed to work efficiently by automatically identifying the shortest route possible for relaying every message.

Even if there are some structural obstructions, clients connect to an alternate router in their range. The Zigbee networks are extremely scalable and support up to 64,000 nodes using a single coordinator. If required, high powered RF radios can be designed for specific applications.

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Is a Wi-Fi Network Secure?

Well, if you have an open network which anyone can access freely because you don’t want to take the efforts or the time to set up some kind of protective mechanism in your access point, its definitely insecure!

But what might actually surprise you is, even if you have taken the basic protective measures, your network might still be insecure! (But not as insecure as the above case for sure ).

When a home user / small business user buys an access point, what do they do to secure their network initially? Enable encryption – Set a pass-code to access their network, set up MAC Filtering (and) hide their SSID – Right?

All of these methods can be broken and your Wi-Fi network can be hacked within no time by using free to download software tools on the Internet! But the time taken and efforts needed to break each of them is different.

When you set up your Wi-Fi network to accept only certain MAC addresses (permanent hardware addresses assigned by manufacturer) without enabling any form of encryption, people can get into your network in no time. Ok, the next-door casual browsing person may not be able to, but any IT aware guy who knows how to search in Goolge can break into your network! Well, that brings in a lot of people inside the scope, doesn’t it?

The issue with MAC address filtering tables is, certain management frames are exchanged between your access point and your PC and they can be easily captured by using some freely available software tools like kismet or netstumbler. They can capture and expose information like SSID Name (Network name), MAC address, IP address, etc. So, all the hacker has to do is to come to a location near your house, capture some packets, identify your MAC address and SSID, change his Laptop MAC address accordingly, and connect to your access point. Its that simple!

Disabling SSID broadcast is a good step, but again the SSID information can always be gained by people who know how to scan / sniff a Wi-Fi network.

Assuming that you enable encryption, if you enable WEP encryption (because you have connectivity problems with other forms of encryption), people can easily crack this encryption within a couple of minutes, as long as they are within the range of your wireless network!

So, there are two more types of encryption – WPA/WPA2-PSK & WPA-Enterprise. The first one is easy to implement and is quite secure for a small office/ home office. But remember,

• WPA/WPA2-PSK Encryption can also be hacked. Its only more difficult.
• The SSID Name and the Passcode-key you select for your network should be complex. Especially the later. People scanning your network might try to break-in by guessing the passcode using automated dictionaries. More complex the pass-code, longer it takes to break the encryption. Of course, in most cases it may not be possible to determine your pass-code key this way.
• One pass-code is shared among multiple users in this method. This is fine as long as you trust them, but if they leak their pass-codes to the guy next door or it accidentally reaches them, it becomes impossible to trace if only authorized users are using your network.
• The pass-codes are generally remembered by the user computers, so if the computer is stolen or accidentally falls in the wrong hands, they can use it to gain access to the network.

The WPA-Enterprise method of encryption is much more secure and virtually impossible to break. But the disadvantage is, it is quite hard to implement. In this method, a digital certificate is configured in each computer that wants to access the Wi-Fi network and individual User-name / Password is given to each user. So, users must generally pass both these steps successfully to connect to the wireless network. In case if you routinely deal with sensitive information in your wireless network, its best to implement the WPA-Enterprise method of encryption.

The next step (or) a simpler method of implementing the WPA-Enterprise is to buy a Wireless Controller and let it manage all the access points in your premises. The Wireless controller can act as a radius server and can enforce security policies. Of course, there are so many other things that a Wireless Controller can do. Some small Wireless Controllers might be affordable for your business, just check it out. So, how secure is your wireless network?

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What is an Ad-hoc Network?

Whether you are using Windows, Linux or Mac laptops, you can connect them to each other over the wireless medium using the built-in Wireless adapter. Generally, a Wi-Fi Network is created by connecting the computers to wireless access points/ wireless routers but Wi-Fi Ad-hoc networks are  created  directly between two Wi-Fi enabled laptops/ systems.  It is also possible to connect more than two devices to the ad-hoc network. In that case, even if two computers are not directly connected, they can still communicate with each other through the common computer/ other computers.

Ad-hoc networks are not a replacement to Wi-Fi networks (Wireless Routers, Access Points, etc) but they are meant for temporary connections between two wi-fi enabled systems. They are used mostly for file sharing, playing multi-player enabled games (or) sharing an Internet connection. Even a wi-fi enabled smart phone can connect to a PC using an ad-hoc network, if the phone supports this feature. Ad-hoc networks are pretty simple to configure and easy to deploy but they have a limited range of few meters.

Generally, one person sets up the ad-hoc network and everyone joins. This network gets terminated when everyone (or) the person who set it up, disconnects from the network. The access to the ad-hoc network can be restricted with a password and the security within an ad hoc network can be enhanced using encryption.

What are the threats posed by Ad-hoc networks?

Sometimes, ad hoc networks are enabled by default in certain operating systems. So, someone in the range of the computer might try to connect to it and access shared documents. Sometimes, users do not encrypt the communication over an ad hoc network. These networks are a delight to hackers (who are within the range of the network) and they try to access and place some malware into the system so that they can carry out further attacks.

If ad-hoc mode is enabled in a laptop and it is also connected to the wireless / wired enterprise network, hackers can connect to the laptop over the ad-hoc network and then connect to the enterprise network to access network resources without the knowledge of the unsuspecting user.

How are ad-hoc networks identified and mitigated?

As you can see above, the threats posed by an ad-hoc network to the enterprise wired / wi-fi network is considerable. Generally organizations prefer to ban ad-hoc networks within their premises. They have a policy to this effect, and new laptops are deployed with ad-hoc networks disabled.

But users can themselves enable the ad-hoc network anytime. One of the ways to monitor for live ad-hoc networks within an organization would be to use air-monitors / wireless intrusion prevention systems. These systems can continuously scan the network and identify any live ad hoc network and report to the administrator.

If required, they can even block the ad hoc network by throttling the communication between authorized clients and unauthorized clients. They can instruct and prevent the authorized systems from communicating with rogue wi-fi clients. They can differentiate between genuine users and rogue users and allow ad hoc networks between genuine users (if required) while simultaneously blocking ad hoc networks involving rogue users, selectively.

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To illustrate the point, let us compare the components used in wired and wireless networks in an enterprise/ organization.

Let us assume that there is an organization with two departments – Department 1 (All Computers connect using the wired network) & Department 2 (All computers connect using the wireless network) – Connectivity and Components for both wired and wireless networks are shown in the above diagram, for each department.

Department 1 is fully wired. So, all the computers are directly connected to the edge switch ports in that department using  Cat 5/6/7 Copper UTP cables. Department 2 is fully wireless. So, all the computers connect (over the air) to the access points. Both the edge switches and the access points connect to the distribution switches of their respective departments.

In turn, these distribution switches connect to the core switch (In the data center) using Optical Fiber Cables (Mostly). For the wireless network, there is a wireless controller (which connects mostly to the core switch) for centralized management of all the access points.

For simplicity, three computers are shown connecting to each edge switch, but let us assume that 15 computers connect to each switch/ access point. So, 3=15, in our diagram!

Wired Vs Wireless Network (Analysis):

So, now let us go to the analysis. The wired network should be rather straight forward to understand, from the diagram. When we consider the wireless network (Department 2), let us list down the changes from the wired network (below):

• In place of three edge switches for the wired network, there is only one edge switch for the wireless network.
• There are three wireless access points to connect all the computers over the wireless medium in the wireless network.
• The individual cables that go to each computer (and hence the other passive components) has reduced in the wireless network because, the cables only go to the access points, and not individual computers.
• Laptops can connect directly to the wireless network with built-in wireless adapters. But in case of computers, additional wireless cards for each computer is required (either internal or external) for wireless network connectivity.
• There is a wireless controller introduced in the wireless network (connected to the core switch) which provides centralized management to the wireless access points.
• The core switch, distribution switches, cables and all other components are same for both wired and wireless network.

So, in conclusion, we can say that a wireless network replaces the wired connectivity in the network edge (where end users connect to the network). The backbone network components (Inter department fiber connections, distribution switches, core switch, firewalls, routers, etc) are the same for both wired and wireless networks.

What about the cost comparison (between wired and wireless networks)?

Think about what we saving by implementing a wireless network in the network edge – The copper UTP cables connecting to individual computers, passive components required for each cable & edge switches/ switch ports.

But also think about the additional cost incurred by introducing the wireless network – Wireless Controller, Wireless Access Points, POE enabled switches (Or electrical power) to each access point & Wireless Adapters (For Computers, not for Laptops).

On a rough estimate, setting up of a wireless network could still cost up to 60-75% of cost incurred in building a fully wired network (Wireless Controllers are quite expensive!), in its place. This is only a rough estimate, and the cost varies based on the deployment conditions.

Except educational institutions and hospitality segment customers (who might prefer a wireless network), most of the customers might prefer the wireless network to be an overlay on the wired network – All the computers connecting to wired network, and the laptops and other guest/mobile devices connecting on the wireless network.

But ever since the wireless controllers have been introduced, some companies have gone fully wireless for their network-edge connectivity requirements. Besides, some devices like printers, specialized industrial equipments etc, require wired network ports.

There are some alternatives like Wireless Mesh Networks & High Power Wireless Radios/ Access Points which reduces the cables and passive components required at the network edge even further, but they are not as popular as the wireless controller based implementations (for larger Wi-Fi based implementations).

So, what about you? What do you think is better? Just a wired network, just a wireless network (on the network edge) (or) an overlay of wired and wireless networks?

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Related Article: Everything you want to know about Wireless (Wi-Fi) Network

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Overview of bluetooth technology:

Like Wi-Fi, bluetooth is a wireless technology that enables data transfer between two devices, or multiple devices (commonly up to 7). Bluetooth is a low power, short wave, short range technology with (relatively) low cost transceivers. There are class 1, class 2 & class 3 bluetooth devices that have a connectivity range of 100m, 10m (more popular) & 1m respectively.

Bluetooth technology supports data rates of 1-3 Mbps, with recent versions supporting much more than that. Line of Sight (LOS) is not mandatory for the bluetooth standard, which is an open but proprietary standard. But LOS increases the range of distance that can be covered by bluetooth networks.

Bluetooth devices operate in the unlicensed ISM (Industrial Scientific & Medical) band in the 2.4 Ghz spectrum like  Wi-Fi devices, but have lesser transmit power than Wi-Fi devices. Its possible for bluetooth and Wi-Fi devices operating in the same channel (sub-frequency) to interfere with each other. But bluetooth overcomes this problem by changing channels (Out of 79 available channels of 1 Mhz wide each) frequently – around 1600 times per second.

Generally, bluetooth adapters are built-into mobile devices, laptops, PDA’s etc. But bluetooth capability can also be added using external USB  dongles. Bluetooth connection between two devices are generally encrypted.

Bluetooth technology allows for multiple devices to connect at the same time (normally up to seven) using a master-slave piconet architecture. But at any given point of time, data can be transferred only between one master and one slave. The master switches between multiple slaves quickly in a round robin fashion to give near simultaneous connectivity.

There are certain specialized bluetooth based enterprise grade access points (like Wi-Fi access points) to connect multiple bluetooth based devices together, to the network and to the Internet. Some of these access points support multiple technologies along with the bluetooth radios. So, these access points might have bluetooth radios, Wi-Fi radios, 3G modems, 10/100 Mbps LAN connectivity, etc in the same device.

As bluetooth devices advertise themselves to the surroundings, they are susceptible to certain vulnerabilities. There are some bluetooth specific attacks carried on by hackers who can take control of bluetooth based devices (To make long distance calls from others cell phone, for example). So, it is suggested to keep bluetooth off, and turn it on only when required. Mandating a PIN based authentication while connecting to other devices might give additional security.

Some enterprise applications of Bluetooth technology:

• The most popular application, which is also applicable to enterprise companies is the use of bluetooth based headsets to attend to mobile phone/ land-line phone calls (hands-free operation).
• A computer can connect to bluetooth based keyboard, mouse over the wireless media.
• Using bluetooth, its possible to connect to and transfer data between a computer to computer, computer to laptop, computer to mobile phone, etc.
• Many bar-code scanners/ point of sale devices connect to the local systems/ network using bluetooth technology.
• There are some printers that can connect to the computers/ laptops using bluetooth technology.
• There are certain heart rate monitoring devices with embedded bluetooth radios that can transfer the real time heart beat information to hand held PDA’s (for example), during sports training sessions.
• Blood glucose meters can communicate with cell phones using bluetooth technology to connect to the Internet and automatically update an on-line patient health database that can be accessed by the doctors.

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Understanding Wireless Frequency Bands:

You might be familiar with the concept of frequency tuning in radio. When you tune your receiver to a certain frequency, you are able to hear the programs from a particular channel. So, when you use an analog rotary tuner to switch channels, you might have noticed that as you rotate the tuner, first a faint sound appears, then you get a strong signal, and then the signal weakens. So, the signals are received (with varying range of amplitudes) over a range of frequencies. When you consider many channels, the used range of frequencies becomes wider.

Similarly, Wireless (Wi-Fi networks) operate mainly in two major frequency bands (ranges) – 2.4Ghz and 5 Ghz. Both are unlicensed ISM band frequencies (Industrial, Scientific and Medical RF band) – Which means, any device / technology can use that band for communications.

2.4 Ghz & 5 Ghz are frequency bands (range of frequencies). The actual communications happen in sub-frequencies called channels, within each spectrum (frequency band). For example, in the 2.4 Ghz spectrum, Channel center frequencies might be like : Channel 1 – 2.412 Ghz; Channel 2 – 2.417 Ghz…… Channel 13 – 2.472 Ghz, etc. A Wireless Radio (on wireless access point) & client radio (wireless client on a laptop) operates in one of these channels to transmit information between them.

Every channel (sub-frequency) overlaps with its adjacent channels. So, Channel 6 for example, might overlap strongly with channels 5, 4 but weakly with channels 3, 2. In the 2.4 Ghz spectrum, Channels 1,6 & 11 are non-overlapping channels. That brings us to the next topic – Interference.

Wireless Interference:

Consider that there are three operational access points situated at a distance of 1 meter from each other (for example). If they operate in channels 1, 2 & 3 (respectively) or channels 1, 1 & 1 (respectively) – there would be a lot of interference that will affect all the clients connecting to these three access points. That’s because, generally access points and clients receive all the communications that are transmitted and reject those that are not in its frequency (channel) of operation. But if different access points operate in same channels (or) adjacent channels, they get confused if messages sent to them were meant for them or not!

But if the three access points are operating in channels 1, 6 & 11 (respectively), even if they are placed very close to each other, there would not be much interference because, the sub-frequencies used by each channel are far apart. In other words, these three channels are non-overlapping channels.

Interference might not allow you to connect to a wireless access point/ network, disconnect you from an existing connection (requiring you to re-connect to the network) or might slow down/ choke the wireless connectivity. Wireless Interference causes noticeable problems with real time applications like voice/ video transmitted over the wireless network. Interference is both a performance issue and a security concern (Rogue Access Points, Wireless DOS attacks, etc).

There are two types of wireless interference – Interference from Wi-Fi (802.11) Sources & Interference from Non-Wi-Fi Sources.

Interference from Wi-Fi (802.11) Sources:

Wi-Fi devices that interfere with the wireless network are – Access Points that are in the range of each other (and operating in overlapping channels); Neighboring Access Points that might be operating in overlapping channels & Wireless Jammers that intentionally operate in overlapping channels.

So, when two access points operate in same channel/ adjacent channels, and are in the range of each other, there would be interference. With 802.11 Wi-Fi based networks and devices, people might still be accessing and working on the wireless network even if there is considerable interference but with reduced throughput levels. 802.11 networks are resilient enough to retransmit the lost packets, but that might reduce the total available bandwidth.

Similarly, the access points across the street or in neighboring office, might as well be operating in the same channel, causing some interference. There are certain wireless jammers which cause interference in the network with the intention of disrupting wireless services.

Since the latest 802.11n network and devices use multiple antennas, they might be in a slightly better position to reduce interference by comparing the received signals from multiple antennas and averaging out the interfering signals.

Interference from Non-Wi-Fi Sources:

Since 2.4 Ghz and 5 Ghz are unlicensed frequency bands (spectrum), a lot of other technologies like Bluetooth, Zigbee & lot of devices like microwave ovens, wireless cameras, cordless phones, wireless headsets, wireless device controllers, etc operate in these frequency bands as well, thereby causing interference to Wi-Fi network communications.

Microwave ovens operate in multiple frequencies (wideband) and consistently interfere with the Wi-Fi devices. Wireless Cameras operate in narrow band and hence interfere on particular Wi-Fi frequencies, Bluetooth headset keeps hopping across the frequency band but still causes interference temporarily.

Even if a complete site-survey is done prior to the implementation of Wi-Fi network, it is still difficult to find out the Non-Wi-Fi sources of interference because, newer/smaller wireless devices are appearing in the market which could be brought by the employees at any time, thereby causing (unintentional) disturbance to the corporate Wi-Fi network.

Detecting and Mitigating Wireless Interference:

5 Ghz is a relatively clean spectrum without much interference from non Wi-Fi sources. But most of the commercially available Wi-Fi network devices operate in the more popular 2.4 Ghz spectrum. It might be better to implement Wi-Fi networks to operate in 5 Ghz frequency band (For this, both the client adapter on the laptops and access point should support 5 Ghz operation), especially with 802.11n high performance networks.

Some vendors fit sensors on access points that detect interference in their channel of operation (if any) and switch to other channels. But this may not be a solution for interference from non Wi-Fi sources. Its possible to reduce the chances of interference by controlling (reducing) the (transmission) power levels of access points. Using multiple/ multi-sector antennas might also improve the SNR.

Wi-Fi Sources: The interference from other Wi-Fi sources are relatively easier to detect, and in some cases even mitigate. The basic principle with Wi-Fi sources is to avoid any neighboring access points operating in the same channel (and adjacent channels). As far as possible, neighboring access points need to operate in non-overlapping channels (Like 1,6,11).

Its quite difficult to monitor each access point manually, and change the frequency of operation manually for all access points (though its possible). Even if they are set manually, if an access point reboots (due to power loss etc), it will choose an arbitrary frequency (channel) which may not be the same as manually set frequency. So, the process (assigning channels manually) needs to be repeated.

To automate this process, a Wireless Controller, that provides centralized management can be used in a network to continuously gauge the channel of operation for all the neighboring access points and adjust their channel settings dynamically. Most of the Wireless Controllers can manage only their own make of access points, but there are wireless management softwares available to manage multi-vendor access points/ controllers.

Non Wi-Fi Sources: The normal Wireless management softwares/ controllers may not detect interference from non Wi-Fi sources (some of them do) but there are specialized spectrum analyzers that can be employed for this purpose. But unlike the Wi-Fi sources of interference, simply changing the frequency channel of operation of access points may not be a solution for non Wi-FI based interference and hence the best way to tackle them might be to physically remove the sources / shield the sources from spreading out, hence restricting them to a certain area.

There are certain open source based spectrum analyzers which can be used for detecting interference like Netstumbler, Kismet, inSSIDer etc. Commercial spectrum analyzers are also available for the same.

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What are the objectives of Wi-Fi Site Surveys?

In short,

• Discover RF Coverage Areas/ Coverage Holes
• Identify sources of RF Interference (internal – microwave owens, cordless phones, satellite dishes, etc; external – neighboring access points, etc)
• Determine the Quantity & Optimum locations for placement of Wireless devices

Why is a Site Survey required for Wi-Fi Networks?

A wireless network, as you know, is comprised of the Wireless Access Points, Wireless Controller, Wireless clients & the passive and active network components that connect them to the LAN backbone. Unlike wired networks where one can say that so many switch ports are required for so many users, its difficult to predict the number of access points (based on the number of users) for wireless networks.

While an access point could connect to hundreds of computers theoretically, there are a lot of factors like bandwidth per user, distance from the access point, type of wireless technology used (802.11a/b/g/n), co-channel/ external interference, roaming, etc that can influence the actual number of users/ quality. So, a wireless site survey is the best way to determine the number of access points and their positions for optimum wi-fi coverage in the area.

How is a Wi-Fi site survey done?

Some vendors take the soft copy of a floor plan, use their site survey software to determine the number and position of the access points; some of them combine the above process with a manual survey to see the possible sources of obstruction on the site. Some vendors do only the manual survey and guess the number of access points required, based on their prior experience!

The best way to do a site survey is to go to the site, place an access point (battery powered, so that it can be moved) at  places where the new access points are supposed to be placed and check for the received power levels using laptops (loaded with a site survey software) at various distances / positions around the AP. Some site survey softwares automatically record the power levels as they move around, while some enter them manually. If multiple frequencies (2.4Ghz/5Ghz) are going to be deployed, the survey could to be done for each frequency  by using multiple client adapters for all the channels to check the actual coverage area/ intensity for each.

In addition to this, the surveyors should get clear information on – maximum users in each area, minimum required bandwidth per user, number of floors, barriers for RF signals (like metal racks, elevators, walls, steel beams, ducts, concrete, asbestos, etc), the number of voice over wi-fi handsets (maximum concurrent calls/ coverage/ roaming), type of applications used on wireless (Mail/ Internet/ streaming media), etc.

What happens after the On-Site Site Survey?

Within a few days of completing the on-site wi-fi site survey, vendors present a detailed report to the customers. Some vendors charge for this report. Among other things, the report includes the number (and model) of access points required for a given site, floor plans with the access points position marked on them, coverage pattern clearly indicated for each access point (through the usage of various colours – each for a particular signal strength value), bill of materials for the wi-fi project along with the cost estimation, etc.

Do check if the vendor has taken the following factors in to consideration, while preparing the site survey report:

• RF interference from neighboring access points (hotspots, AP’s from neighboring office, etc)
• RF interference from non wi-fi devices like microwave ovens, cordless phones, satellite dishes, etc
• Access Point coverage pattern on multiple floors (Its possible to reduce the total number of access points if  the AP’s from top and below floors are considered)
• For sites with primarily outdoor coverage, its possible to integrate web based applications like Google earth to prepare (and present) more accurate results
• Total number of users currently/ expansion planned for the near future/ user density in each floor
• Channel Interference from other access points/ overlapping of all AP’s where voice roaming is required
• Passive/ Active components to connect to the LAN backbone – cables, cable routes, POE switches, racks, etc
• Basic coverage at some places (like lawns) / Powerful coverage at places with higher user density (like conference rooms)
• Desired (minimum) rate of bandwidth per user
• Length/ width / number of floors/ wi-fi obstacles/ radio types (802.11a/b/g/n)/ outdoor coverage/ wi-fi leakage outside the building, etc

Limitations/ Dis-advantages of Site Survey for Wireless Networks:

No matter how accurately the wireless site survey is done, its not possible to accurately determine the usage patterns/ expansions/ external interferences in the near future that might affect the wireless coverage. As mentioned earlier, over provisioning is not a good option with wireless networks – even though wireless controller takes care of the channel interference, there are only limited number of channels (especially in) 2.4 Ghz band & 5 Ghz band.

It is also very difficult to replicate the whole set-up for wireless network, during the site survey.  Even if that is done, the results obtained when a large number of concurrent users are simultaneously accessing the wireless network would be quite different from the site survey results. One more disadvantage is the fact that most of the site survey softwares cannot accommodate/ suggest directional coverage (using directional antennas) for special cases and it might have to be done manually.

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Related Article: Wireless (Wi-Fi) Networks – Basics

Normally, when a wireless client (PC, Laptop) is switched on, it will try to probe the nearby area for access points for a particular SSID (SSID is like a name for the network, which is advertised in order for users and clients to associate with the access points). In this scenario, if a hacker is nearby (perhaps in the car parking), he could use access points with high power (gain) antennas with the same SSID as the corporate network SSID and respond to such client probe requests with a valid probe response. As the wireless clients generally associate with an access point with the highest power (signal strength), it can get associated to the access point belonging to the hacker.

Once the honeypot association is made by the attacker with a valid client from an internal corporate network, he can find out a lot of  information about both the client and the network and use them to launch further attacks like Man In the Middle attack, Wireless Denial Of Service (DOS) attack, etc. So, as you can see, wireless honeypot itself is not an attack but it paves the way for other attacks.

Using Wireless Honeypot to detect Hacker Activities:

This is an interesting application of wireless honeypots and can be used by the administrators to detect and divert wireless hacker activities. In this method, a low cost access point/ soft-access point without any authentication/ encryption is deployed on a separate network (other than the corporate network) preferably with a few clients (PC’s) and some wireless traffic running between them. If any hacker is casually looking for open/ weak wireless access points to associate and attack, this honeypot will surely lure him in to it. That is the purpose of a honeypot!

Once a hacker connects to the wireless access point, all his activities could be monitored. Administrators could study the methods used by such hackers and see what information they are trying to capture/ which worms/ attacks they are trying to inject in to the network. By doing this, the motive and the methodology used by hackers can be studied. Moreover, a honeypot AP could (at least temporarily) keep the hacker engaged and alert the administrator so that the actual network can be safeguarded.

What is a Wireless Man In The Middle (MITM) Attack?

A Man In The Middle (MITM) attack is actually a continuation of the honeypot attack wherein a hacker would lure a wireless client to associate with his honeypot access point (either by increasing the honeypot access point’s signal strength using high gain antennas (or) by inducing a denial of service attack on the nearest legitimate AP with the highest signal strength) and utilizes his Laptop/ computer as a proxy server where all the communication between the wireless client (user) and the target host server goes through this proxy server. Initially, the target host server would be a public server placed on the Internet but if proper information is available, it could be an internal server as well.

So, obviously the attacker would hope that once a wireless client connects to his wireless network, the first thing it wants to do is to connect and browse over the Internet. Because, if the client wants to communicate with an internal server, the hacker cannot redirect the communication to the internal server as he cannot connect to it, yet. For the wireless client, Internet can always be connected through the hackers proxy server (installed in his Laptop) using a wireless data card (for instance).

This process is slightly more complicated. First, the wireless client sends a request to connect to a particular server in the Internet using a domain name. These domain names are resolved in to IP addresses using DNS lookup tables. At this moment, the hackers laptop (which is also connected to the same honeypot access point, sends a fake IP address (and perhaps even a fake certificate) , which is essentially same as the IP address of the hacker. When the client sends more requests, these are accepted by the proxy server installed in the clients laptop and forwarded over the Internet to the real public servers. When the proxy server gets the response from the Internet, the same is again transferred back to the wireless client  which had requested it originally.

So, the wireless client thinks that the responses are coming from the public server directly, but the responses are actually forwarded through the proxy server of the hacker. Now, since all the information flows through the proxy server in his laptop, the hacker can get a lot of information including web-mail user-name/passwords etc.

How to detect a Honeypot/ Man In The Middle (MITM} Attack on the wireless network?

One of the ways in which a Wireless Intrusion Prevention System detects a Honeypot/ Man In The Middle (MITM) attack is by recording the BSSID (MAC address of access points), ESSID (Wireless Network Name), Channel and Signal Strength information for all the access points in the wireless network.

If any combination of those parameters do not match for an access point, then there is a chance that this AP is a Honeypot AP. The channel information is important because, even if the honeypot AP uses the same ESSID and BSSID information, the channel would most probably be different (Especially if the legitimate AP is taken down using a Denial Of Service attack as the honeypot AP needs to operate away from that channel).

But there is a chance that the hacker makes the honeypot AP operate in the same SSID/channel as the legitimate AP.  In these cases, the signal strength information is compared in addition to all the other parameters. A honeypot AP will have totally different levels of signal strength when compared to the legitimate AP. So, this information can also be used.

Some Wireless Intrusion Prevention Systems check if the access point is present in both wired as well as wireless networks. A honeypot is generally placed outside the wired network, and hence this factor helps in identifying them. For stopping this attack, the wireless connection between the honeypot access point and the wireless client could be disconnected by using disconnection frames (reverse DOS attack).

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