Computer Identity

joyjoy
Posted:
in General Discussion edited January 2014
Can someone tell me, when I log into a forum using 1 computer only but using 2 different accounts can the administrator of the forum I logged into identify that I am using only 1 computer. I am connected to the internet via DSL.

Your help would be very much appreciated. Thanks.

Comments

  • Reply 1 of 18
    Quote:

    Originally posted by joy

    Can someone tell me, when I log into a forum using 1 computer only but using 2 different accounts can the administrator of the forum I logged into identify that I am using only 1 computer. I am connected to the internet via DSL.

    Your help would be very much appreciated. Thanks.




    The admins of a forum (such as this) can only see what your web client broadcasts to the internet. That means your IP address, the browser you're using and some other stuff (such as referrer information). The computer identity, as far as I can tell, can't with any certainty be ascertained by webservers. But, chances are, the IP address of your computer won't change by switching users, allowing them to conclude with reasonable certainty that you're using the same computer.



    edit: your!=you're
  • Reply 2 of 18
    Quote:

    Originally posted by pensieve

    The admins of a forum (such as this) can only see what your web client broadcasts to the internet. That means your IP address, the browser you're using and some other stuff (such as referrer information). The computer identity, as far as I can tell, can't with any certainty be ascertained by webservers. But, chances are, the IP address of your computer won't change by switching users, allowing them to conclude with reasonable certainty that you're using the same computer.



    edit: your!=you're




    Thank you Pensieve. One more thing. is the IP address of one company common to all its subscribers? Can the system admin then just conclude that the 2 accounts are subscribed in the same IP company? What about our "computer name"? Can they see that? Can they ascertain that only 1 computer unit is being used and not a network sharing the same IP?
  • Reply 3 of 18
    joyjoy Posts: 9member
    Hey guys no replies yet?



    Pls. give your 2 cents worth if you know something about this topic.



    Thanks.
  • Reply 4 of 18
    joyjoy Posts: 9member
    Hey guys am not doing anything illegal here am just trying to test if a guy is faithful.
  • Reply 5 of 18
    der kopfder kopf Posts: 2,275member
    Quote:

    Originally posted by pensieve

    But, chances are, the IP address of your computer won't change by switching users, allowing them to conclude with reasonable certainty that you're using the same computer.



    Except of course for the fact that most DSL users (and cable users) are doomed to dynamic DNS, meaning that you get a different IP address each time your DSL modem 'logs on' to your ISP. Therefore, it would be really hard for any administrator to pinpoint your two user instances. Especially since, for instance, company lans often have 1 IP address for 5 or ten (up to 50 and more) computers. So there's always that consideration. It could even be two people in the same family using the same connection.



    Additionally, you could disconnect and reconnect your DSL connection (between your modem and the ISP, not between the modem and your computer) to make sure you won't be spotted.
  • Reply 6 of 18
    der kopfder kopf Posts: 2,275member
    Quote:

    Originally posted by joy

    Can the system admin then just conclude that the 2 accounts are subscribed in the same IP company? What about our "computer name"? Can they see that? Can they ascertain that only 1 computer unit is being used and not a network sharing the same IP?



    Didn't see this before.



    They can indeed conclude that (see above). Especially if they are willing to believe that two computers have the exact same OS and browser installed (which is probably common enough).



    Your computer name is restricted to your LAN (local area network). It doesn't go past the DSL modem (or, in fact, the WAN connection of your router).



    They can. I saw a white paper once that showed a (very advanced) technique for counting the hosts between a NATted LAN (meaning: counting how many users are connected to a router from the other side of the router), by keeping track of the ACK numbers in the TCP headers (and, more specifically, if they are continuous or not). However: I think nobody running a forum has that kind of software, nor does anybody need it (it is used mainly by ISP who allow only one computer per DSL/cable connection).



    So in short: it is not impossible to find this out, but it is VERY hard.
  • Reply 7 of 18
    joyjoy Posts: 9member
    Thank you very much. Some more tips?
  • Reply 8 of 18
    amorphamorph Posts: 7,112member
    Quote:

    Originally posted by joy

    Thank you Pensieve. One more thing. is the IP address of one company common to all its subscribers?



    Sort of. If you're connecting to an ISP from a home account, you're given an IP from a range of IPs called a block that your ISP has purchased. For example (and the numbers are made up here), your ISP might have purchased 65.128.47.0 through 65.128.48.255. Each number can range from 0 to 255, so this gives the ISP 512 addresses to hand out to subscribers. Anyone with one of those addresses is connecting through that company. The IP changes when you reconnect with the ISP, and/or after a timeout period set by the ISP. In this case the ISP knows exactly which customer is assigned to which IP at any given time, but good luck getting that information without a subpoena or a court order.



    If you're dialing into a company's internet access, all bets are off. Your IP is probably hidden behind NAT - network address translation - which makes all traffic from an entire network appear to come from the same IP. Some home networking products, such as the AirPort Base Station, can also provide NAT, in which case every machine accessing the internet through the Base Station appears to have the same IP.



    Quote:

    Can the system admin then just conclude that the 2 accounts are subscribed in the same IP company? What about our "computer name"? Can they see that? Can they ascertain that only 1 computer unit is being used and not a network sharing the same IP?



    In the most common case, that's all that I (for example) can discern with 100% reliability. It's possible to be almost completely certain of duplicate accounts by watching IP assignments over time, but at this point you're using heuristics rather than any certain knowledge.



    The "computer name" is not knowable unless you've allowed someone to contact your machine to find that out and they do - on the Internet, your name is your IP.



    It is impossible to tell from looking at an IP whether that IP is assigned to a particular machine or to a subnet behind NAT. Sometimes you can do a DNS lookup to discover interesting things about the nature of an IP, such as whether it's a dialup account (this is courtesy of the ISP using self-documenting names like 'dialup-user-489.dynamic.isp.net', not because of the nature of the IP itself).



    As der Kopf points out, you can find out a great deal with the right tools and knowledge of the networking protocols and the network itself. The things that my friend the senior network engineer can discover by glancing at a traceroute are amazing. But using the information available to the average web forum admin, there's not much there.
  • Reply 9 of 18
    joyjoy Posts: 9member
    Quote:

    Originally posted by joy

    Thank you very much. Some more tips?







    I saw in one of the forums when the administrator told 2 members that he knows they are just using one computer. How do you think he found out? Do you think that the reason is because they are using a dial up connection?
  • Reply 10 of 18
    der kopfder kopf Posts: 2,275member
    Quote:

    Originally posted by joy

    der Kopf,



    I saw in one of the forums when the administrator told 2 members that he knows they are just using one computer. How do you think he found out? Do you think that the reason is because they are using a dial up connection?




    I'd point to what Amorph said: heuristics. Maybe that administrator wasn't even right at all, and they were just behind one WAN connection? In any case, I'd probably try to see if the users always connect close (in time) to each other with the same IP, to find out if the one member is just logging in as one user, posting, reading, whatever, logging out and logging in as the other user. If it's always like that, you may be in that situation. It's more a work of educated guessing than scientifically pinpointing.



    Maybe Amorph could tell you more.



    Also: dial-up is the proto-typical case of dynamic DNS, so each time you dial in, you will most definitely get another IP address.
  • Reply 11 of 18
    amorphamorph Posts: 7,112member
    Quote:

    Originally posted by joy

    I saw in one of the forums when the administrator told 2 members that he knows they are just using one computer. How do you think he found out? Do you think that the reason is because they are using a dial up connection?



    That might have been his reasoning, but you can get an AirPort Base Station (for example) with a built-in modem, and share it between any number of machines. The ABS will ask for one IP and use NAT to share it with every machine in its network (which could theoretically comprise well over 200 machines, although I'd love to see 200 machines sharing a dialup connection...).



    So while his leap of logic that dialup account -> modem attached to computer is statistically fairly safe - far more people dial up through internal modems than through modems built into routers - it's still a heuristic, and he could still be wrong.



    der Kopf: I think you meant that dialup is the prototypical case for dynamic IP. Dynamic DNS is another matter entirely.
  • Reply 12 of 18
    joyjoy Posts: 9member
    Glad to be a member of this forum. You all have been very helpful.



    Yes der Kopf, you are correct, that is what I've been doing. I' know better now.



    Thanks.
  • Reply 13 of 18
    joyjoy Posts: 9member
    Thank you vmuch guys! I can't believe that there are still people like you who help others even if you don't know them. You've been very heplful to me!



    To people like you I say GO AND MULTIPLY!!!
  • Reply 14 of 18
    der kopfder kopf Posts: 2,275member
    Quote:

    Originally posted by Amorph

    I think you meant that dialup is the prototypical case for dynamic IP. Dynamic DNS is another matter entirely.



    Oops. My bad!



    Anyway, glad to have been of help.
  • Reply 15 of 18
    defiantdefiant Posts: 4,876member
    now go and change your custom title to 'Professor of Almost Everything'
  • Reply 16 of 18
    der kopfder kopf Posts: 2,275member
    Quote:

    Originally posted by Defiant

    now go and change your custom title to 'Professor of Almost Everything'



    Hey, I knew that, I just didn't proofread.
  • Reply 17 of 18
    joyjoy Posts: 9member
    I checked my "Internet Connect" and it has 2 adresses the first one: it said: Status: connected to 123.456.78.9" -this doesn't change when I turn off and turn on the LAN, but the other address which says "IP Address 987.654.321.012" - this is the one which changes everytime. What does this mean?
  • Reply 18 of 18
    baumanbauman Posts: 1,248member
    Quote:

    Originally posted by joy

    I checked my "Internet Connect" and it has 2 adresses the first one: it said: Status: connected to 123.456.78.9" -this doesn't change when I turn off and turn on the LAN, but the other address which says "IP Address 987.654.321.012" - this is the one which changes everytime. What does this mean?



    The first IP - the one it says you are connected to - is the IP of your ISP company. The second is the IP of your computer. And it makes sense that it changes every time if you are on a Dynamic IP address system - which most systems are unless you pay more for a static address.
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