Add Me!Close Menu Navigation

My technical corner about Linux, Perl, programming, computer networks and network security

Add Me!Open Categories Menu

What can see your Internet Service Provider?

Did you think ever what’s happen when you browsing the Internet?


Flow of information in a typical computer network is displayed on the image below:

Let me introduce you about couple things. The field “Your computer” represents a computer, a smartfon, a notebook, a printer, a TV tuner – each network device which can communicate over a computer network. Most people are unaware that not only typical computer or a notebook can use a computer network, but all of these things and many more are classified as the computer in my flow chart.

The next square represents network devices such as hubs, switches, routers. These devices are dedicated to support a network connection between network devices. A typical computer with proper software can do the same thing like typical routers, but I will show a typical scenario in most cases. In the typical scenario network devices are very small devices with many sockets and lights.

The square named “Internet” isn’t required any explanations, I think. The arrows show a network flow direction between these abstraction layers.


The most important thing on the flow chart is the square represents the main router of your ISP. Because it’s important, the square was marked of the red frame by me. But, why this is so important? As you can look, all the network traffic is crosses throught this place. A gateway is a router which decides where should be send packets from its networks.

Routers (gateways) in network are worked similiar like postmans. If you want to send an envelope with letters, you insert all letters into an envelope, describe the envelope and then you send this. A postman see what an address is written on the envelope and if receiver’s address isn’t belonged to his area, then he relay the envelope to another postman who may know this area (first postman thinks that).  So, the envelope will be checked by another postman. If the address also isn’t belonged to another postman area, then he relay this to another postman, etc… If the address is belonged to some postman area, then he deliver the envelope to a receiver.

All of these postmans can read the address on your envelope, because they have to know, where the envelope should be relayed. Now, you may replace world “postman” with “routers” and you know what routers work – exactly the same way.

Can you see any threats here? Your envelope can be opened by each postman and your letters may be read. Postmans shoudn’t do this of course. A glue isn’t good protection. But the same way may be occurred in network devices. If you don’t use a crypthographic trasmission protocol or you don’t encrypt your files or messages, then it may be read by these devices and administrators of your network. Remember.



Ettercap is a program which can answer to the main question in this article. If you manage some network and you are an administrator (ISP) then you may see something like this:


Ettercap is a network sniffer which can easily reads some information from unencrypted protocols or older version of encrypted even. This program is free and your ISP on your default gateway may use it or something like this – be vigilant! Almost each webpage was visited by you may be know, e-mails and many other services as well.

Leave a Reply

You must be logged in to post a comment.