This lecture will be devoted to protocols and networking.
We'll analyze the three lowest layers of the S.I. model.
We'll start with a physical layer.
The security risk that the physical layer is most susceptible to comes from the denial of service attack.
The result of this attack is the authorized users cannot use certain systems services
as we know the physical layer is the basis of all higher layers.
It's easy to conduct a successful attack on the physical layer.
Unfortunately few technological solutions can prevent that.
The piece of news that you see in the slide provides a good example.
The story is about a 75 year old Georgian woman who cut off most of our mania from the internet.
Scavenging for scrap metal.
She found a transmission cable.
She thought it was a copper cable but it turned out to be a fiber optic cable.
Obviously she didn't manage to get even $25 for it.
From our perspective the most important bit of this story is the woman managed to defeat the security
measures of all the computers in our mania with a shovel.
DNS attacks are a serious vulnerability of the physical layer.
Wireless networks are especially susceptible to this problem but this will be the topic of another lecture.
The second serious vulnerability of the physical layer comes from unauthorized access to the medium.
The picture you see above shows that you shouldn't blindly follow stereotypes.
One such stereotype is that fiber optic cable connection is always more secure than a copper cable connection.
It's generally accepted that a copper cable signal is easy to intercept because the transmission emits
an electromagnetic field.
Moreover many people think that a fiber optic cable transmits lightwaves which are immune to electromagnetic
interference and thus the signal cannot be intercepted without cutting across the cable.
And this in turn can be easily detected.
This is not entirely true.
The device you see in the slide is widely available on the Internet.
It costs about $1000 if you can access the fiber physically.
You have to bend it in such a way that you see in the picture and attach it to the device.
After that the fiber emits wave light outside.
When the light gets reflected from the wall of the cable the light loss is about 1 percent a sensitive
detector could intercept the signal escaping from the fiber.
Then you just have to convert the signal back to the electric form and connected device to the computer.
That's how you get an optical fiber cable monitoring system.
Of course there are devices that can detect that the fiber is bent.
If there's an automated attack someone has probably already invested money to develop an automated defense
against the attack.
However the devices for the signal interception monitoring costs much more than a thousand dollars.
If someone can get physical access to the medium through which the signal is sent that can intercept
all the data that passes through that medium.
In many cases they can also modify it in real time.
For example the moment it was sent the data at the far end of the fiber is different from that which
was sent for example your subtotal might have changed or a piece of hostile code was added to the binary
file.
You should trust the data source.
However after the data passed through a medium that was accessed by an unauthorized person.
The end result may be different from the one expected such attacks represent a serious risk for modern
computer systems.
No medium ensures protection against data interception.
The physical layer doesn't provide any technology that would allow data encryption nor does it include
any solution that would enable the receiver to authenticate the sender of the data package.
The two main threats the physical layer is susceptible to come from DNS attacks which can be as simple
as unplugging a network cable and interception and modification of the data sent through the medium
without the use of technology.
You have to restrict access to the medium to do so.
Companies employ security firms install digital locks et cetera.
Monitoring the surroundings of the company's premises may also provide effective protection consequences
of a malfunction can be limited by duplicating the most important connections.
But these are the only three available methods of physical layer protection.