-: So, in this lesson, I wanted to show you 2 2
what some of these antennas look like 3 3
with more of a hands-on approach. 4 4
So, let's go ahead and start with what's called 5 5
an omnidirectional antenna, and this is what you have 6 6
in most of your wireless access points 7 7
and most of your wireless devices. 8 8
So, if I take, for instance, this old cellphone. 9 9
This old cell phone has a Wi-Fi connection 10 10
inside of it, built in. 11 11
It actually is an Android cellphone 12 12
and it has the ability to either receive a wireless signal 13 13
through Wi-Fi or put one out as a hotspot 14 14
and then allow other devices to connect through wifi to it 15 15
and then go out through its cellular connection 16 16
to get access to the Internet. 17 17
Now, you'll notice, when I was talking about this cellphone, 18 18
I mentioned it's omnidirectional. 19 19
And that makes sense for a cellphone 20 20
because as you're walking around, 21 21
you don't know which direction 22 22
the signal's going to be coming from. 23 23
So, instead, it's going to send and receive data 24 24
both up and down, left and right, 25 25
forward and back, in every single direction, 26 26
with equal power to be able to connect 27 27
to the local wireless access point 28 28
or the local cellular tower, 29 29
depending on which frequencies we're using. 30 30
Now, this is the same thing that happens 31 31
with your wireless access points, too. 32 32
So, for instance, if I take this old 33 33
wireless access point from Netgear, 34 34
you'll see this is actually a combination device 35 35
of a router, a switch, as well as a wireless access point. 36 36
There's no external antenna. 37 37
Instead, they're using an internal omnidirectional antenna 38 38
just like that cellphone did. 39 39
And so, in every single direction, 40 40
we're going to be sending data out 41 41
to be able to get data out equally in all directions. 42 42
So, if I want to make sure that this doesn't bleed over, 43 43
if I'm in a townhouse or an apartment, for instance, 44 44
I'd want to put it closer to the center of my apartment, 45 45
because if I put it on one of the walls, 46 46
it's going to go out in every direction, 47 47
including through the wall and into my neighbor's apartment. 48 48
And so, you might want to consider 49 49
that from a security perspective. 50 50
Now, some of the more expensive wireless devices 51 51
are going to give you the ability to change out your antenna. 52 52
So, for example, we talked earlier 53 53
about this combination device that I got from Verizon. 54 54
And inside this one, we did have the ability 55 55
to connect a different antenna. 56 56
So, normally, it's going to come with an antenna like this, 57 57
which is a standard little whip antenna 58 58
and this is considered an omnidirectional antenna. 59 59
So, as I connect that on there, 60 60
I'm going to be able to send data out 61 61
in every direction, all 360 degrees. 62 62
Now, this is a rather small antenna, 63 63
so it's not going to have as much power. 64 64
Maybe I wanted to get my signal to go out further. 65 65
Well, I can actually change that. 66 66
And I can take that antenna off 67 67
and I can put on a bigger antenna. 68 68
And with the bigger antenna, I'm actually going to be able 69 69
to send data out a little bit farther than I could before, 70 70
because the longer the antenna, 71 71
the more propagation you're going to get from it. 72 72
Now, also, when I'm doing wireless attacks 73 73
and wireless hacking and pentests, 74 74
I actually have a wireless card 75 75
that I use with my laptop and that has the ability 76 76
for me to change the antenna, as well. 77 77
And so, I would take this wireless card 78 78
and I would screw on whichever antenna I want. 79 79
So, if I want more distance or more power, 80 80
I can go ahead and use an omnidirectional antenna 81 81
like this, screw it on, connect this through USB 82 82
back to my laptop, and now, I have this antenna 83 83
radiating out in every direction. 84 84
Now, I've spent a lot of time talking 85 85
about omnidirectional antennas, 86 86
but what do you do if you want to 87 87
make it go in a single direction? 88 88
For example, when I'm doing wireless pentesting, 89 89
often, omnidirectional is not the best way to go 90 90
because when you're putting power out in all directions, 91 91
you're limited in how far you can go. 92 92
But if I can focus my power in just one direction, 93 93
that's called unidirectional, I can actually focus 94 94
all the power out the left side of the antenna 95 95
or the right side of the antenna. 96 96
And that way, I can push all of the power one way 97 97
and no signal goes out the other. 98 98
So again, going back to the apartment example, 99 99
if I'm up against the right wall of the building 100 100
and I have a directional antenna pushing 101 101
all the power out left, it's going to go into my apartment 102 102
and not into my neighbor's, because we have that right wall. 103 103
That's using a unidirectional antenna. 104 104
And we have unidirectional left, 105 105
unidirectional right, and things like that, 106 106
so we can choose which direction we're going to be using. 107 107
Now, the other thing when we're dealing with antennas 108 108
you have to think about is what are some 109 109
of the other types of antennas that are out there? 110 110
Besides the standard unidirectional and omnidirectional, 111 111
uni meaning one, omni meaning all, 112 112
we also have things known as parabolic. 113 113
Now, parabolic are a special type of unidirectional. 114 114
Parabolic is going to give it a different curvature 115 115
to the way the signal's going to go out, 116 116
and it's most often used with microwave signals, 117 117
as well as satellite TV signals, 118 118
as you could see here on this particular antenna. 119 119
Now, this is a DIRECTV antenna 120 120
on one of my neighbor's houses 121 121
that I drove by and took a picture of for you. 122 122
And you can see that curvature 123 123
of the dish which is going to focus 124 124
the energy up and towards the satellite 125 125
and not out in every other direction. 126 126
Finally, I want you to consider this other antenna here. 127 127
This one is actually in the UHF band, 128 128
which is a frequency band that we use, 129 129
and it used to be used a lot for TV before we had cable. 130 130
You'd have UHF and VHF. 131 131
Now, with this antenna, you can also see 132 132
that it is a very directional antenna. 133 133
You could see how it's pointing 134 134
in one direction, almost like an arrow. 135 135
That's going to allow it to get a further reach to that signal, 136 136
to that TV transmitter that's sending it out. 137 137
Now, do we use these anymore? 138 138
Well, sometimes. 139 139
These actually can be used to point 140 140
and push a wireless signal over a longer distance. 141 141
So, if you're in a business park or a campus setting, 142 142
you might see some of these antennas on top of buildings 143 143
pointing from one building to the other, 144 144
using this unidirectional antenna. 145 145
And in this case, this is actually known as a Yagi antenna, 146 146
Y-A-G-I, and it allows them to have a very directional, 147 147
focused beam going from one building to another. 148 148
So, if you hear the term Yagi, 149 149
that is going to be something that is a directional antenna, 150 150
unidirectional antenna, going one way. 151 151
Now, if you hear about parabolic, 152 152
I want you to think about that satellite TV, 153 153
that curved dish that's pointing 154 154
that directional back towards the satellite. 155 155
And if you think about omnidirectional, 156 156
I want you to think about these embedded devices. 157 157
Things like your wireless access point 158 158
or things like your cellphone 159 159
or things like your wireless card 160 160
with a long antenna like this one. 161 161
But this is just the idea. 162 162
There's different types of antennas 163 163
used for different situations, 164 164
and it all depends on what you're going to do. 165 165
Now, for the exam, you want to be able to know 166 166
when you should use an omnidirectional antenna 167 167
or when you should use a directional antenna 168 168
or when you should use something that attaches 169 169
to the side of a building, like a patch antenna, 170 170
which is a small, circular dish 171 171
that is able to go on one side of the building to another, 172 172
and they can point at each other in a directional manner. 173 173
These are different types of antennas 174 174
that you may come across when dealing 175 175
with wireless networks and they're important 176 176
to understand before you take the exam.