how computers communicate, internet protocols (ip) and firewalls
TRANSCRIPT
Knowledge Base
How computers communicate, Internet Protocol (IP) and Firewalls
Most computer to computer communications use
the Internet Protocol (IP).
How computers communicate
Most computer to computer communications use
the Internet Protocol (IP).
This basically sends data information cut up in
chunks. We call these Packets.
How computers communicate
Most computer to computer communications use
the Internet Protocol (IP).
This basically sends data information cut up in
chunks. We call these Packets.
Each Packet is identified with both the source and
the destination addresses. You can therefore think
of them as a shipping box containing a message.
How computers communicate
In the IP protocol, each computer has it’s own
address.
How computers communicate
But the Internet is a network… of networks!
Billions of addresses are in play, making for a
complex environment.
How computers communicate
There are tons of mechanisms in place to manage
addresses, but ultimately we can make abstraction
of that and concentrate on the fact that a
computer can communicate with another when its
address is known.
How computers communicate
But the address is just that, an address.
What’s extremely important in IP is the conduit.
How computers communicate
But the address is just that, an address.
What’s extremely important in IP is the conduit.
The conduit can carry a lot of information to an
address, and we mean a lot!
How computers communicate
But the address is just that, an address.
What’s extremely important in IP is the conduit.
The conduit can carry a lot of information to an
address, and we mean a lot!
A good analogy can be made with Cable
Television. A single cable (conduit) can carry many
channels to your house.
How computers communicate
But the address is just that, an address.
What’s extremely important in IP is the conduit.
The conduit can carry a lot of information to an
address, and we mean a lot!
A good analogy can be made with Cable
Television. A single cable (conduit) can carry many
channels to your house.
In fact, in the IP protocol there are 65535 channels!
We call them Ports.
How computers communicate
So we have packets of information, being sent from
one computer to another.
How computers communicate
So we have packets of information, being sent from
one computer to another.
Travelling on a conduit allowing for 65535
“channels”.
How computers communicate
This is one channel, receiving a flow of packets…
How computers communicate
This is one channel, receiving a flow of packets…
Now just imagine 65535 channels…
How computers communicate
Going back to our previous diagram, we see two
networks connected to the Internet.
Malicious users
But the Internet is not just composed of nice people,
hackers are either trying to infect your computer
with viruses, or to get access to your data
Malicious users
This is why firewalls were created, a mechanism was
needed to allow only authorized traffic into your
company’s network.
Firewalls
This is why firewalls were created, a mechanism was
needed to allow only authorized traffic into your
company’s network.
They are often depicted by a nice brick wall, but
the analogy is misleading.
Firewalls
We must allow some traffic through…
Firewalls
…while rejecting most of the rest
Firewalls
Really not how we see a brick wall, is it?
Firewalls
Its much better to visualize the firewall as a mail
sorting facility, but with a highly regulated flow.
Firewalls
Its much better to visualize the firewall as a mail
sorting facility, but with a highly regulated flow.
You can create rules for any of the 65535 ports.
Firewalls
Its much better to visualize the firewall as a mail
sorting facility, but with a highly regulated flow.
You can create rules for any of the 65535 ports.
There rules can restrict source AND destination
addresses.
Firewalls
Let’s say that you do not want any packet destined
to port 21 to go through the firewall, you would
have a rule like:
Firewalls
Port From To Action
21 * * DENY
Let’s say that you do not want any packet destined
to port 21 to go through the firewall, you would
have a rule like:
The stars indicate that any address will match this
rule.
Firewalls
Port From To Action
21 * * DENY
Let’s say that you want to allow your users to
browse the internet (incidentally, this uses port 80),
you would have a rule like
Firewalls
Port From To Action
80 LOCAL * ALLOW
Let’s say that you want to allow your users to
browse the internet (incidentally, this uses port 80),
you would have a rule like
In this case, the LOCAL keyword indicates that all
of your local addresses are allowed. Meaning the
addresses of your company’s computers.
Firewalls
Port From To Action
80 LOCAL * ALLOW
So imagine a huge
table of rules…
Firewalls
Port From To Action
21 * * DENY
80 LOCAL * ALLOW
115 * * DENY
3389 LOCAL * ALLOW
22 LOCAL * ALLOW
443 LOCAL * ALLOW
8181 EXTERNAL 192.168.10.10 ALLOW
* 192.168.10.1 * DENY
34534 EXTERNAL 192.168.10.234 ALLOW
80 LOCAL facebook.com DENY
443 LOCAL facebook.com DENY
80 LOCAL pinterest.com DENY
443 LOCAL pinterest.com DENY
80 LOCAL ad.doubliclick.net DENY
443 LOCAL ad.doubliclick.net DENY
54322 EXTERNAL 192.189.10.199 ALLOW
22 LOCAL 165,10,23,33 ALLOW
1433 LOCAL 165,10.23.33 ALLOW
20222 EXTERNAL 192.168.10.143 ALLOW
…and imagine a really efficient mail sorter
Firewalls
…and imagine a really efficient mail sorter
Looking at each packet Source address…
Destination address…
Port…
Firewalls
…and imagine a really efficient mail sorter
Looking at each packet Source address…
Destination address…
Port…
Searching for rules for that port in the rule table
Firewalls
…and imagine a really efficient mail sorter
Looking at each packet Source address…
Destination address…
Port…
Searching for rules for that port in the rule table
Then ruthlessly applying the decision, for the Deny
rules, it just drops the packet
Firewalls
So firewalls are that big mail sorting facility
Firewalls
So firewalls are that big mail sorting facility
Allowing some traffic to go through
Firewalls
So firewalls are that big mail sorting facility
Allowing some traffic to go through
But protecting you by dropping packets that may
have been sent by malicious users
Firewalls
So firewalls are that big mail sorting facility
Allowing some traffic to go through
But protecting you by dropping packets that may
have been sent by malicious users
If you need to go through a firewall to perform some
work, you may have to use a Virtual Private Network
(VPN), please consult our presentation on that
subject.
Firewalls
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