-: Proxy Servers.
A proxy server is a device that acts
as a middle man for your clients.
For example, if you're at work
and you wanted to connect to diontraining.com,
your work computer's likely going to go
from itself to a proxy server
within your company's LAN.
And then, that proxy server makes the connection
to Dion Training to get the information that you requested.
And then it will hand it back to you.
This middle man approach allows the company
to log everything that's being requested,
who made them, and to filter out things
they don't want you to access.
There are four types of proxies in use today.
IP Proxy, Caching Proxy, Content Filter,
and Web Security Gateways.
An IP Proxy is used to secure a network
by keeping machines behind it anonymous.
When your work computer decides
to connect to Dion Training through the proxy
in my example above, my server doesn't know
which particular computer is actually connected
to it from your company's network.
All I see is the proxy server itself.
This is because your proxy is using NAT
to translate your request from your machine
into a request from the proxy.
If you had 20 different computers on there
trying to access my web server,
it would still just look like one machine
to my server, not 20.
The next type is called a Caching Proxy.
Caching Proxies are used to attempt to serve
client requests without actually connecting
to the remote server each time.
Let's say that you went to my website
at diontraining.com, and then your coworker,
five minutes later, tried to go to diontraining.com,
just like you did.
Well, the proxy, if it's using a cache,
is going to be able to keep a copy
of my webpage from the first time it fulfilled your request.
Then, when your coworker requested it,
it would simply give it from its cache
instead of going and getting a new copy from my site.
This will allow your company to save
on bandwidth costs, and increase the speed of delivery
for your coworker, because it already has it locally,
inside your network.
The most common caching proxy is known as an HTTP Proxy,
which attempts to cache the web pages that are visited
by users, such as the example I just gave you.
Caching proxies are not as effective
as they used to be, though,
because we all live in a Web 2.0 world
with lots of customized content being served up to us.
So, for example, if you went to Facebook.com
and your coworker went to Facebook.com,
both of your Facebook feeds look
drastically different, don't they?
This is because you each get different information
based on your friends and your likes and your desires.
So, caching here isn't very helpful
because of this Web 2.0 structure.
Also, most caching proxies only keep a copy
of the information they get for about 24 hours.
And after 24 hours, they're going to go back out
and request a new copy to ensure
that they get the latest information.
Now, to simplify the installation
and configuration of a caching proxy
in your web browser, there's a special type
of file called a PAC, a Proxy Auto-Configuration file.
This file contains the settings needed
for a host to connect to the proxy server.
Unfortunately though, these files are subject
to modification, and could be used to redirect
the user to an attacker's control proxy
instead of your organization's.
For this reason, it is better to disable
the PAC files, and manually configure your proxy settings
on your host machines, or you can push these out
using a global policy object, or GPO update.
Now, the third type of proxy is called
an Internet Content Filter.
These are used in large organizations
as a way to prevent users from getting to stuff
that they don't want you to access at work.
It can filter out all types
of different Internet activities,
such as websites that aren't allowed to be accessed,
email services they don't want you to get to,
or even instant messaging.
For example, many of the organizations I work for,
we blocked web mail services like Gmail and Yahoo
because we didn't want people accessing those at work.
We also blocked gambling websites,
and pornography, and even Facebook.
Now, some of these are because
they went against our organizational values.
So, that was the case in gambling and pornography.
While others were blocked because we didn't want people
hindering productivity at work,
things like Facebook and that web-based email.
Again, this is something that your organization
can decide, what they want to use, and what they don't.
The final type is called Web Security Gateway.
And this type of proxy acts as a go-between
for devices that will scan them for viruses,
filter out contents like ads,
and then can act as a data loss prevention device as well.
This type of proxy is looking at what's being sent out
of the network, and what is coming back into the network
to ensure that it aligns with your organization's policies.