-: Telephony devices.
Telephony is a term that's used for a device
that provides voice communication to your end users.
Originally, telephony was used in networks
to make connections with the outside world
such us through your modem.
So, a modem was this old device that we used to use
that would allow us to modulate and demodulate
digital information into an analog signal
that could transmit over a standard dial-up connection.
So, if you used AOL as a dial-up connection
way back in the day,
you would put your phone line into your computer,
it would take your ones and zeros,
convert them into signals of sound,
and transmit that over the phone line.
Now, modems were a great attack vector, though,
from the security perspective.
And for the Security+ exam,
you need to know the concept of war dialing.
War dialing is simply when an attacker
starts dialing random phone numbers
to see if any modems would answer on the other side.
So, a lot of servers back in those days
will have dial-up modems
so that remote technicians could dial into the server,
gain access, and make changes to due support.
Well, if I was an attacker
and I started dialing random numbers like 555-1234,
nobody there.
555-1235 and just keep adding numbers,
eventually, I'll find some server that answers.
And if they do, I now have a way into that network.
So, how do we protect modems in our systems
for any dialog resources that we may have
from this type of thing like war dialing?
Well, one of the main things to do
is use a callback feature.
If you still have modems, which most of us don't
in our networks anymore, but if you do,
you want to make them set so that when somebody calls in,
they would then hang up
and the modem, if it recognize that phone number
based on caller ID, will then call them back
and initiate the connection.
This will verify that the person is who they think they are
and who they say they are.
Now, you always want to also use some form of authentication,
like a username or password.
But preferably, you want to use something more complex
like two-factor or multi-factor authentication.
The best practice, though, is to do what most of us have done,
and that's eliminate modems where possible
and switch your remote access
to using things like an SSH connection over VPN tunnels.
Now, while it's great to try to eliminate all your modems,
sometimes you still have old systems
and you simply can't do that.
If you have to maintain a dial-up modem for some reason,
you want to make sure you keep that dial-up number a secret.
And so, somebody's going to have to work hard
to be able to find it
and be able to get into your system.
Again, if you have a dial-up modem,
you want to use good authentication.
You want to be able to use things that will help prevent it
like callbacks and other things to help secure it,
because these are prime targets for attackers.
Now, the next type of telephony equipment I want to talk about
is a PBX system.
A PBX equipment is something you're going to find
much more often in your networks
than you are going to find modems.
A PBX system stands for a Public Branch Exchange.
Essentially, this is the telephone system
that runs all of the internal phone lines for your company.
If you're sitting in your office
and you want to call your accountant inside the office
and you dial the last four digits of his phone number
only to get him, that internal call
is being routed through your PBX system,
through that public branch exchange.
Now, attackers like to target PBX systems too,
and it's not necessarily to try to break into the system
and be able to get information out of us,
but instead, it's because they want to get free long distance.
Now, some of us use our cellphones
and we get free calling across the entire United States.
So, long distance doesn't seem like a big deal.
But, if you want to start placing calls
all the way around the world,
and you can break in to somebody's PBX system,
they're going to get the bill for it and you're not.
So, that's why an attacker would do this.
Now, how do you secure your PBX system?
Well, one of the best ways
is to actually mount it in a locked room
inside your telephone area.
By putting it in a locked room,
it means only authorized maintenance technicians
can get into it and touch the system.
Also, you want to disable any remote access to that PBX
and any remote access ports
because again, that's where attackers
are most commonly going to be accessing your PBX from.
Now, well, PBX systems are still fairly common in industry.
They are getting replaced in large numbers
in favor of VoIP.
What is VoIP?
Well, it's Voice Over Internet Protocol.
VoIP is much cheaper than the traditional PBX system
and it's a lot more secure and easier to run
if you can figure it properly.
Some organizations will actually run
two different networks now.
One for data and one for the VoIP network.
And this will allow them to be able to have
two separate networks that gives you more security.
But a lot of organizations
try to take the easy or cheaper way
of combining them both onto a single combined network.
And now, you have VoIP devices
sharing the network the data devices are onto,
like your computers.
Now, if you do this, you want to make sure
you put at least the VoIP devices
on their own VLAN and their own subnets
to help create some of that separation
and segmentation we talked about earlier.
Now, VoIP works by relying on IP phones,
software, and VoIP gateways.
An IP phone is simply a physical device
that looks like a regular telephone
but takes a network cable into it
as opposed to a phone cable.
This thing connects back to the VoIP gateway,
which will make the conversation happen
between your phone and the remote destination
that you're trying to call.
To secure VoIP devices,
you want to update the device's firmware
because these IP phones are devices after all,
and they do get firmware updates
that have patches and security
when they've been hacked.
You also want to make sure you're using good authentication,
good encryption to make sure maintaining the integrity
and confidentiality of the phone calls that you're making
between your VoIP device, the VoIP gateway,
and then the remote destination.
Availability is another concern you have with VoIP.
When you're dealing with VoIP,
and we talked about this back in Network+,
you have to make sure implementing good quality of service.
This isn't as much a security concern,
but because availability is part of the CIA triad,
we do want to be keeping that in mind as well.
VoIP takes a lot of bandwidth
and it takes a lot of good quality of service,
meaning, it needs a short delay inside the communications.
Otherwise, your phone calls don't sound good.
And that can become leading to a denial of service.
And so, making sure that you have
the proper quality of service
put into your networks
will allow your VoIP devices
to communicate more securely,
more quickly, and have better availability.