Overview of Wireless Networking Tutorial

2.1 Wireless Terminology

Before we get into the particulars of wireless hacking and security, I think it's helpful that we go over few basics about wireless technologies. Now, we don't assume that you don't know anything about wireless because, wireless security is a bit of an advance topic We know that you probably implemented a sample and installed wireless networks but it's still helpful to go over a few basics about wireless just to refresh your memory or to cover a few things that you may not Remember or may not have learned. First, let's talk about a few wireless terms to help get us started and then throughout the next couple of sessions we'll look at just some wireless basics, we'll refresh our memories about wireless standards and topologies and so forth. First of all, the very basic, a wireless client. Now wireless client is any device that needs to access a wireless network that communicates with another device or a wireless access point. A wireless client could be something like your laptop. Your desktop PC, your tablet, even your cell phone. All these devices have wireless network cards in them that help them to connect to other devices. The next thing we'll look at is Wireless Access Point. In an infrastructure, in other words a larger wireless network that consists of wireless clients and other wireless devices, we have the Wireless Access Point or WAP. That's the centralized connection point. That wireless access point can help connect many different wireless clients together. It can also connect those wireless clients to the Internet or another larger. Network, whether it be another wireless network, or a wired network. And we'll talk about WAPs as we go through the next few sessions. Now there's also something called a Service Set Identifier, or SSID This is essentially just the name of the network, the particular wireless network that you're a part of, and connecting from. This is just like a network name for a wired network. Frequently wireless networks are identified by their SSID. Now there are some security considerations with the SSID and it being broadcast out so that everyone can see it. And we'll talk about those a little bit later. Now let's talk about the two modes that we typically see wireless clients connect with. There's Ad Hoc mode and Infrastructure mode. And we'll be taking about this a little bit more in depth as well over the next few sessions but let me tell what they are first. The Ad Hoc mode is essentially where I have at least two wireless devices connect to each other Not through a wireless access point. They just talk one on one to each other. That's ad hoc. Doesn't require much set up. The infrastructure mode, however, requires a wireless access point of some sort, and different clients have to be configured properly to connect to it and to each other. Some other terms we'll talk about. And this is by no means comprehensive. We'll cover a lot of new terms as we go through the course. But a few other terms we'll discuss are authentication, encryption, and the 802.11 standards. Authentication is essentially the ability for us to identify ourselves to the wireless network. Our clients, even our own personal selves through user IDs and passwords. Authentication is necessary to make sure that we know who is connecting to our wireless network. Encryption helps us by scrambling the data so that it is not easily readable when we connect through a wireless network. Now, there are considerations with plaintext data Being transmitted over wireless. So we want to make sure that encryption's involved. That is a serious security issues with wireless networks. And we'll talk about that throughout most of the rest of the course. The final term we'll talk about before we get to wireless basics are the 802.11 standards. And these are a set of standards produced by the IEEE. That basically dictate how wireless networks will connect to themselves, what protocols they'll use, what hardware they'll use, and so forth. And we'll go in more depth on the 802.11 standards over the next few sessions. So this is just a basic introduction to some of the terms you'll see that we're going to talk about throughout the course.

2.2 Wireless Basics

Now let's cover some of the wireless basics, and talk about how wireless networks are set up. Now of course we assume that you've set up wireless networks before, and probably administered them. However as we've said it's good to cover the basics just to remind you of how things work. Now wireless devices do use different hardware and technologies to connect to each other. And to other networks. However, most of these technologies, including protocols, services, and so forth, are basically the same as wired networks. Now, most wireless technologies are implemented at the bottom two layers of the OSI model. Model. If you go back to your basic networking days and experience in knowledge, you'll remember that the OSI model is a seven layer model that talks about how networking works, and how different protocols are implemented throughout the OSI model. The bottom two layers are the data link layer and the physical layers.This is what we find in most wireless technologies or particular device work. Now wired technologies also use these layers as well but in different ways. Most wireless devices and networks Are based upon the 802.11 standards that are put out by the IEEE. Now these standards provide four different ways to connect, authenticate, and encrypt data with wireless devices. And we'll cover those Those standards as we go through the course, particularly the security standards. Now in addition to the 802.11 standards, wireless uses most of the other common protocols at higher layers in the OSI model, particularly TCP/IP which we know is the Internet standard to connect to the Internet as well as other networks. Now, there are usually three ways that wireless topologies connect with each other. And we'll talk in depth on those as well. First of all, there's Ad-Hoc. And this is typically a peer-to-peer device connection. In other words Two tablets connect to each other wirelessly so that they can play a game, or a laptop and a tablet, or even your cell phone and your laptop, something like that. Usually these connections are easy to set up and are done so on both devices. We also have the infrastructure mode. And this is where a wireless client connects to an access point. Which serves as the central connection point for many wireless devices. It also serves to connect to a larger network, maybe a wired network, maybe a local area network, or maybe even the internet. This infrastructure mode is how we see most wireless networks implemented in homes and in businesses. Here on the screen, this is a basic infrastructure network. We have a Wireless Access Point here and different wireless clients or devices that can connect to the Wireless Access Point of course. Now we have configuration settings that have to configured on both the clients and the Wireless Access Point, and that's actually the topic. More in depth on another session. Now let's talk about the third kind of connection, and that's the bridged network. A bridged network looks sort of like an infrastructure network except that it usually connects two wireless networks together via access points. Or it can link two wired networks together using a wireless connection. So you have two wireless networks that have to talk to each other or to a larger network. How do we set this up? We can use a wireless bridge. And that's what's pictured here on the screen. As you can see, we have two disparate wireless networks, each with an access point, each connecting to a switch or a router and then clients, and they're connected to each other wirelessly. So data can be sent From network to the other. You can also use this type of network to connect to a larger network, such as a service provider network, or local area network in a business, or the internet. Those are some wireless basics, and we'll talk more about some of the fundamentals of wireless as we go through the next few sessions.

2.3 Wireless Hardware

Now let's discuss wireless hardware basically the fundamentals of the different pieces that connect wireless networks with clients and APs together. There's several pieces to consider when we deal with various devices. Now this is just an elementary type of discussion of course. There are a wide variety of wireless hardware devices out there and we'll discuss a lot of those throughout the course. The basic kind of wireless hardware there is, is the wireless network card or NIC. This NIC is typically built into most devices. Such as laptops, tablets, cellphones and so forth. Now previously this was not the case when wireless first came out You had to buy a separate wireless card that you would put in your PC or even attach to your laptop, via USB or an add on card. Now, these days of course, most wireless hardware is built into the device itself. So you typically can buy a PC or a laptop with wireless built in already. In fact, that's one of the primary features that you would look for when buying a mobile device is its wireless capability. Now the wireless network interface card obviously is installed in the device to enable you to connect to wireless networks. Without this, you can't connect. You will typically also see wired network connections, such as ethernet ports, in a device as well, such as a laptop or a PC. You typically won't see those in a PDA or a tablet. You'll only see wireless. You'll see owner cards that may look to be PCMCIA cards, and those are specifically for laptops. Or you may see USB network cards out there that are for USB ports on devices such as laptops and PCs. And you may still buy those and use them if the onboard wireless card goes out, breaks on you and you need to replace it. But typically this was used for older devices that didn't have one. Now here's a typical wireless card that you may put inside a PC not a laptop and you'd slide this into an available slot, install it. And either the wireless drives would have to be installed or the operating system may pick it up on it's own And install them for you. We typically don't see this a lot anymore, because most PCs do come with cards. Some don't, so you may have to buy a wireless card to install or, if the wireless card ever goes bad, you'll have to buy a replacement for it. Now let's look at wireless access points. The wireless access point is a centralized connection device. And it basically is used to receive the signals from the wireless clients and forward them to other clients on the network, or to other networks including the Internet. Now this device is similar to a wired hub or switch. In fact, in addition to having the wireless capability, a lot of wireless access points that you can buy also have wired connection points. So it may serve as a basic switch as well. You may have five or ten ethernet ports for wired clients on there as well. And an uplink port so it can connect to another device, such as another switch. Or maybe a DSL modem or cable modem or something like that. Now you usually buy these as dedicated devices that are manufactured specifically to be access points, but you can turn computers into access points as well. Probably not done too often except maybe by hobbyists or in very specific situations where you need the device to do other things. Such as firewall functions and so forth, but, you can do it. We see a lot of Linux boxes that are easily turned into access points. Here on the screen, are a couple of Commercial/personal grade access points. You could use these for small businesses or your homes. And they're typically considered SOHO devices. Small office, home office devices. Now some of the larger devices for commercial grade enterprise type of applications Are obviously bigger, have more antennas, have switch ports and so forth on them, and are highly configurable, and may also be used in a larger infrastructure where they talk to wireless devices, such as other access points and repeaters. So, there's different hardware out there that you can see, out there in the wireless world.

2.4 Wireless Transmission Methods

In continuing our discussion on wireless basics, I think it's helpful for you to know the different wireless transmission methods that are out there. Now you may be thinking why would you need to know that for security. But actually understanding the more technical things involved with transmission and signalling and so forth may help you later on during your security career. You may discover new attacks that take advantage of these transmission methods, you may use technologies to your advantage, but it's also just helpful to know how things work. Now wireless devices use one of several different transmission methods This is typically based upon the 802.11 standard that they implement. Three methods that we'll discuss are DSSS, FHSS, and OFDM. The first is Direct Sequence Spread Spectrum or DSSS, now some of the older wireless LANs used Spread Spectrum technology for transmission And we also see some of the newer technologies that we'll discuss in a moment that use Spread Spectrum. Now DSSS is used in almost all of the old 802.11b implementations. We don't see this anymore, because we don't see a lot of 802.11b anymore, thankfully, but you'll still see it out there. Now the other spread spectrum is Frequency Hopping Spread Spectrum or FHSS, and its in less ure than DSSS. However we do see it in one important implementation And that's 802.15 which is the bluetooth standard. So bluetooth devices use Frequency Hopping Spread Spectrum. Now, FHSS transmissions jump between several frequencies at a pre-determined rate or interval. So they're a little bit different from the SSS. Now, one important thing is that DSSS and FHSS do not interoperate. The next one we'll discuss is Orthogonal Frequency Division Multiplexing, or OFDM. Now this is more modern and it's typically used by the newer technologies 802.11 a, 802.11 g, and so forth. Now 802.11a is an older technology, but OFDM has made its way all the way to the newer 802.11g networks. This transmits data using several different carrier waves at once. Now each of these wave carries a part of the message that's broken down and sent. So that's where the frequency division comes into play. Now the older spread spectrum vs. OFDM. Let's take a look at the comparison there. Spread spectrum technologies are able to easily penetrate walls, they're less prone to interference and they offer Greater distances a little bit more in fact where as OFDM typically offers a higher data rate as one we see that used in a lot more newer technologies because we want to higher data rate. However, it's over smaller bandwidth. It has somewhat of a resistance to interference and it has more non-overlapping channels. Now this is just a basic overview of some of these transmission methods. We'll talk a little bit more about them as we need to throughout the course.

2.5 802.11 Standards pt. 1

Now let's continue our discussion on wireless basics. And discuss the 802.11 standards. The original 802.11 legacy standard came out in 1997 loosed by the IEEE. Notice there's no a,b,g,or n after it. It was the first standard top right in the 2.4 gigahertz band. Which is the ISM band or industrial, scientific, and medical band. The data rates were typically pretty low for that standard, one or two megabits per second, and obviously, that's one reason why we don't use it today, is the data transmission and bandwidth requirements we have today would not suffice for the original 802.11. Now it was it was replaced by the newer standards because of different signaling methods so forth. This standard actually allowed FHSS or DSSS transmission methods. The A standard came out in 1999. And unlike the original, it used the 5 GHz band of the unlicensed national information infrastructure band. It offers speeds way faster, up to 54 Mbps and used OFDM. Now the 802.11a typically is not interoperable with any of the other standards. One good thing about it is it's not really subject to interference from other wireless devices, things that fall in 2.4 gigahertz range, for example. Cellphones, microwaves, wireless and cordless phones. Or any other 802.11b device because again due to the frequency range. Now the a standard when it first came out more expensive than the b standard. And partially because of this it was less widely adapted. It did not make its way into the commercial world very well or private home use world. We did see it a lot in industrial, medical, police and so forth, get adopted there. Also it wasn't adopted very well in Japan and Europe because there were no international standards, really, for use of the 5 GHz band. Another drawback of the A standard and any standard that uses OFDM is it has a shorter range, typically 30 to 50 meters. Now one thing we'll point out is that when we discuss these ranges that's subject to interpretation because the standard will tel you what the range ought to be. But understand that there could be variances in equipment and power on the equipment. And things like objects that are in the way, and so forth that could limit your range, obviously. And you may even get a better range than what the standard lists sometimes. Now the B standard came out in 1999, the same time as the A standard. However, it was more widely adopted because there was a lot more equipment out there for it. Manufacturers were just producing the equipment a lot more than the a standard equipment, and it cost a lot less. Now, it's not compatible, again, with the a standard. One thing that's interesting about it is that it offered a lower speed, whereas a offered 54 megabits per second, the b standard only offered up to 11. Now you would think this would have affected a widespread adoptability, but it didn't. Again, cost is what drove B standard being adopted faster. Now it operates in the ISM frequency range, the industrial, scientific, and medical range, 2.4 gigahertz, which unfortunately is the same frequency range that we see things like Cordless phones and microwave ovens operate in. Because of the same frequency range it usually is interoperable with 802.11g devices. In fact we may see a lot of devices out there that are BG devices, both standards. This was the first Wi-Fi Alliance approved standard and the Wi-Fi Alliance. Essentially a group of vendors that got together, that agreed to be interoperable, to have their devices work together. With this standard we also saw WEP come out, the Wired Equivalent Privacy and this was an attempt at securing Wireless networks. Now, the b standards uses DSSS type of signaling, so it has greater range than the a standard would, because again, OFDM methods typically offer a shorter range. The b standard was approximately 100 meters, again, give or take because the power set on the device Or the ambient conditions such as weather rain so forth. Or even things like obstacles in the way of the transmission path and so forth. It could be more or less than a hundred meters.

2.6 802.11 Standards pt. 2

Now let's discuss the 802.11g Standard. This came out a little bit later than the A and B standards. B came out in '99. And g came out in 2003. So, the I triple E and the market, the vendors Head time to look at the wireless standards, and decide on some changes, some things they really wanted to fix. So G came out, and it was actually widely adopted very quickly because of several factors. The bandwidth. The different transmission method available, the widespread availability of equipment and the available types of security that you could put on a G device. Actually even though it came out long time ago, it's still one of the current standards we use in typical home and business environments. You'll still see a lot of G out there. It operates in a 2.4 GHz or ISM range the same as B does. It also provides speeds up to 54 megabits per second. The same as a does. And unfortunately like the a standard which uses ofdm it has a shorter range. Right around 15 meters or so That's actually inherent to wireless standards that use the OFDM transmission method. Now because it works in the same ISM frequency band, it's interoperable with 802.11b standards. In fact, most of the devices that we see that use g. Are b devices. In fact, we'll also see b/g/n devices out there. Again, it uses OFDM as its transmission method, so it unfortunately has a shorter range. One other drawback to G is that it suffers from interference from other devices within the same ISM frequency range. Anything that operates in the 2.4 gigahertz range. Which is a very popular range for consumer electronics. Cordless phones, microwave ovens, other b devices and so forth. Now let's talk about wireless N. Wireless N has had a long rocky road to implementation. It was a draft for a very long time, but that didn't stop Wi-Fi vendors from producing wireless n draft devices. So they tried to get a jump on the standard before it was actually officially released. Those devices still typically work very well with the published standard. As a matter of fact, anything that goes wrong with those devices, and there's usually An update of firmware to fix anything that was caused by the difference between the draft standard and the final standard implementations. So its pretty much to lay the standards for wireless networks for commercial and home private use wireless networks. It pretty much replaces the 'g' standards but its also interoperable with the b standard And you will see a lot of devices out there that are b and n. Now a lot of people probably didn't rush out to buy n when it came out, if they were using g already. So it something that could slowly replace the g devices out there. It's not necessarily a run out and grab A new wireless router just because wireless N came out. Although some people probably did. One of the reasons that people really like the N standard is, look at the data rates. 200 to 600 Megabits per second. Now that's theoretical of course. Again, it depends on the different hardware you're using, how much power it has, the weather conditions, obstacles, and so forth. So that is theoretical. But it's still very good. Now the range again, because it uses OFDM, is around 50 meters. One thing about the end devices, is they can operate at either 2.4 or 5 GHz. You can switch those frequencies around. However, I would tell you that you must have all of your devices in the same frequency range. So if you switch it to five GHz, you're going to have to go out and buy cards That are compatible with the 5 GHz frequency range to put in your laptops, desktops, and so forth. So it may or may not be practical to do this. Those are the basic A, B, G and N standards we've talked about over the past two sessions. and later we'll talk about even more 802.11 standards as they apply to the different facets of wireless networking, such as security and so forth.

2.7 Other Standards

[SOUND] Now let's briefly just touch on a couple of the other standards out there that we have for 802.11. And these are by no means all the 802.11 standards or all of the ones that we'll continue to discuss throughout the course, but these are just a few you probably ought to be aware of. Aware of. Now some of the other 802.11 standards include quality of service standards. That's the 802.11e. So if you had services that require a lot of high bandwidth, or a lot of dedicated bandwidth. That would use quality of service such as video streaming. Voiceover IP and so forth. All of that over wireless. The standard would become effective, wouldn't need to be used. 802.11f addresses roaming and multi-vendor interoperability. So that when you roam with wireless devices between different access points, it's actually interoperable and you can do it seamlessly. Now the H standard covers the European use of the 5 GHz band. Again, this was a new standard. When A first came out, it wasn't widely adopted in Europe because there was no standard that covered this and now the H standard does. A popular standard that we're going to talk about later is the Bluetooth standard, of course. And this has kind of become the defacto wireless standard for small wireless devices, personal area networks where we do media streaming and voice calls and so forth from cellular devices. To other devices or between media servers and so forth. So we'll talk about this a lot. That's that 802.15.1 standard. We also have the Wireless Access Protocol or WAP. Now don't confuse WAP here. In context with WAP of wireless access point. Unfortunately, some of these acronyms mean several different things, so we'll point that out when we need to. The Wireless Access Protocol is actually a standard that covers wireless applications on. On devices. And there's actually several layers to the Wireless Access Protocol. Among them is the Wireless Transport Layer Security Protocol. And we'll talk about that a little bit later as well. Then there's the 802.1X standard. This is a popular standard that's not specifically tied to wireless. It can be used in wired networks and other types of networks as well. And it covers port based authentication and encryption. One of the big uses for this in wireless networks is not only do we have device authentication, but it's made possible through 802.1X. It also interoperates with some of the other security protocols we'll discuss later, such as EAP, EAP-TLS, and so forth. Again, we'll talk about all those later. So you don't have to worry about that for the moment.

2.8 Wireless Topologies

Let's discuss Wireless topologies. Now Wired and Wireless topologies are somewhat different. We know that Wired topologies are driven by how the network is logically and physically laid out. With respect to its wiring. Now wireless obviously not restricted to a physical layout. Because there's no wires involved. There's no connection end points that restrict it to certain places. For wireless topologies typically refer to what kind of infrastructure. Whether it's ad hoc or infrastructure mode and how clients connect to the wired network through the access point Now let's take a look at some typical wired topologies and then we'll compare those to how wireless looks. These are the things that we expect to see in a wired network. And some of these are older topologies such as ring, but we also have things that are typically. Used in smaller to larger networks. Bus networks are still used, line networks are used occasionally but not very often. What we typically see is mesh or partial mesh and star networks. Partial mesh networks we may see in particular segments of the network where there has to be some redundancy involved. And as you can see, From the mesh, the second diagram from the left, and that's a partial mesh. That some of these have multiple connections to other hosts. And that's for redundancy purposes. Now in a fully connected, or a full mesh, as we can see in the fourth little diagram from the left. The fully connected is where every Host is connected to every other host so that we'll have a full connection in case one connection goes down. So there is full redundancy built in. You don't see that very often in wired networks to be honest. Every now and then you might see it. What we typically see is the star and that's the third diagram from the left on the top row. And that's how most wired networks are logically and physically a star. Now the other topology down at the bottom line intrigue, we don't see a lot of that, occasionally we do, really depends upon the design of the network. The point of the wired topologies is that there must some sort of physical connection between something say the host and the network hub or network switch Or even a another host. So it's very restrictive in design. This is an example of wired star. How you might see it and this is a very simple design here. Typically you'll see this implemented. In larger networks and it'll be a little bit more complex. You'll have several switches and hubs connected together or to a centralized router. But this is the basics. So you have a centralized switch in the middle and each host whether it's a Mac or a laptop or whole pc. Will have a connection to that switch and that switch will basically will be the central concentration point Now here's example of how wireless might work. Now you see something very similar but notice the dotted line there. The dotted line indicates that there's no physical cable or physical connection. What we have here on the left hand side is a wireless access point and you have different types of clients connecting to it. Now these are all connecting wirelessly. Now the reason it looks to be in a star Or infrastructure mode is because the clients do connect to the central access point. So, in that respect, it kind of is a star, because they all have a connection to the central access point, even though it's not wired. The other thing, really, though is that once a wireless client has authenticated to the AP, it can actually talk directly to other hosts. So there really is sort of a mesh involved. There could be a situation where the access point goes down, and the host can still talk to another host, because they've exchanged keys and so forth. Now in an ad-hoc mode, you have actually a full mesh. A full logical mesh because every host can talk to every other host. And there may be one host or several on the network, but you don't have the benefit of an access point to authenticate so each host has to authenticate to every other host. But that gives you a full connection to each one and there's nothing to go down that would cause a connection problem. So there's redundancy built in. So this is a little bit about Topologies and as far as security goes, it has to do with it somewhat but now extraordinarily. Typically the security aspects of Topologies we see, are whether there's an access point involved or whether it's an adhoc connections. It's really from a security perspective what we have to worry about this point

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  • PMP, PMI, PMBOK, CAPM, PgMP, PfMP, ACP, PBA, RMP, SP, and OPM3 are registered marks of the Project Management Institute, Inc.

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