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How can an ISP track their clients?

Posted on 2010-11-16
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Last Modified: 2012-05-10
Hello,

I have a curious question, how can an ISP track their clients that use 3G usb wireless modems specially that we knows that the users get a dynamic IP. Any idea?
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Question by:david875
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by:BitsBytesandMore
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When it is a computer the one requesting an IP, the computer needs to identifiy itself with its MAC address before it can be offerred an IP address... with a smartphone/modem it needs to provide the IMEI in order for the systems to check if it is authorized or not.

Bits ...
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by:BitsBytesandMore
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Expanding a little on the above, the MAC address, IMEI (smartphones also have MAC addresses), is something like a serial number, or, a unique number that no other device is supposed to have (they are assigned at manufacturing). The manufacturers are provided with a batch of numbers to use and they imbed these numbers in the device to be available when requested.

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by:david875
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For exemple my ipconfig shows my usb modem as :
Suffixe DNS propre à la connexion :
Description . . . . . . . . . . . : WAN (PPP/SLIP) Interface
Adresse physique . . . . . . . . .: 00-53-45-00-00-00

But this is not my MAC address, because it's not my NIC MAC, the provider just gave me that MAC, so i believe that it is IMEI that exist on the back of the modem, but how can the ISP track that i used such IP in a specific time in case i changed it and got a new IP. they have sort of History ? I mean IMEI match an IP?
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BitsBytesandMore earned 500 total points
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Yes... they DHCP server (the device that assigns the IP addresses) on the provider side keeps a database of all the IP addresses it has assigned and to who it assigned it to. It uses not only the MAC address but the IMEI as well (this is why you can change the sim card from one phone and use it on another one).

So, in order for you to get service you get an IP addresses based on the phones MAC address, but in order to get service you get it based on your IMEI..... the 2 combined allow you to have/or not Internet access....

The MAC address is the physical address of the hardware itself. The moment you change your IP address for any reason, the USB Modem will request from the DHCP server a new IP, your provider will receive this request and tell the modem it has one available for him (or not) and offer it to your modem. If your modem accepts it then the DHCP server will provide it and keep track of it.



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by:BitsBytesandMore
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Some people... on a computer network, change manually their IP addresses. When they do this, sometimes they assign an IP address that is already in use.

When this happens, the computer will receive a message that the IP address is already in use and report the conflict. The  system will remain in conflict until the problem of duplicate IP addresses has been solved.

I'm not sure if you can change it manually on a smartphone or a 3G USB Modem, I have never tried it but I guess you probably can figure a way (everything is possible).

Bits ...
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by:david875
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ok thank you
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by:david875
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Just one Last thing, i have recently remarked that i was using an IP that my ISP assigned to me and have been used by someone else, when i go to rapidshare for exemple and try to download something it says, someone already downloading from this IP address, i think the provider has PAT behind the firewalls not NAT exactly, what you think? so how can they track this thing? based on port?
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by:BitsBytesandMore
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If you are using and application such as "Hide My IP" or other anonimizer or if you are trying to download several files simultaneously, the RapidShare servers detect this and do not allow it.

When I've tried to download using "Hide My IP" from RapidShare, I'm usually trying to load multiple files. If the IP I got assigned by the anonimizer has just been used (or is currently downloading) and the other person who is using it, requested another IP to beat the system and do another simultaneous download, then RapidShare would allow him the 2nd download but the first download is still using the first IP address provided thus why you are getting the message.... it is very common for heavy downloaders to come across this....

Bits ....
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by:BitsBytesandMore
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As for your question regarding PAT... from Wikipedia (they word it much better than I can dream of):

"...Port Address Translation (PAT) is a feature of a network device that translates TCP or UDP communications made between hosts on a private network and hosts on a public network. It allows a single public IP address to be used by many hosts on a private network, which is usually a Local Area Network or LAN.

A PAT device transparently modifies IP packets as they pass through it. The modifications make all the packets which it sends to the public network from the multiple hosts on the private network appear to originate from a single host, (the PAT device) on the public network.

PAT is a subset of NAT, and is closely related to the concept of Network Address Translation. PAT is also known as NAT Overload. In PAT there is generally only one publicly exposed IP address and multiple private hosts connecting through the exposed address. Incoming packets from the public network are routed to their destinations on the private network by reference to a table held within the PAT device which keeps track of public and private port pairs.

In PAT, both the sender's private IP and port number are modified; the PAT device chooses the port numbers which will be seen by hosts on the public network. In this way, PAT operates at layer 3 (network) and 4 (transport) of the OSI model, whereas basic NAT only operates at layer 3
..."

In other words... Yes, this could be the case.

Bits ...

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by:david875
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the ISP can know your passwords when you log in to your email or paypal or banking access point? passwords are stored?
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by:BitsBytesandMore
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Well, that is a whole different subject and question...lol.

The answer: maybe. This type of communication is normally encrypted.

Bits ...
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by:david875
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yes i know :D if they can access my email then this would be a serious problem :D
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