Is it possible that two systems on the Internet can have same IP?
My ISP provides a dynamic IP address binding for my connection. I attempted to download a certain file on rapidshare and I was prompted: Your IP address is already downloading a file... I have not initiated a download. More precisely, I have never logged on to the Rapidshare website since I last installed my current OS...
What's the problem?
Multiple IPs on the Internet?
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lockedin2code
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Multiple IPs on the Internet?
We're bugs if we don't share knowledge! What have you got to give?
IP addresses are unique identifiers, so no.
Think of it like a telephone number.
An exception might be that two computers on the same network are manually assigned the same IP address, but the results would be unpredictable, perhaps one or both would be unable to connect at the same time, or perhaps they would just experience intermittent connection issues... and this really doesn't apply to your situation.
If you were using a proxy, and someone else was using the same proxy it might show up to rapidshare as a second connection from the same IP address.
Think of it like a telephone number.
An exception might be that two computers on the same network are manually assigned the same IP address, but the results would be unpredictable, perhaps one or both would be unable to connect at the same time, or perhaps they would just experience intermittent connection issues... and this really doesn't apply to your situation.
If you were using a proxy, and someone else was using the same proxy it might show up to rapidshare as a second connection from the same IP address.
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bad_brain
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lilrofl, it's also possible to use the same IP for different hosts if they share the same gateway and use NAT.... 
so if you are not part of a private network that shares the same gateway, or, as lilrofl said, you use a shared poxy, there are only 2 possible reasons:
- error on the RS-side
- someone is abusing your connection
ok, another reason could be that your ISP is a VERY small one and another customer of that ISP used the IP right before you, then he disconnected, you connected and got the IP instead...but in this case RS should say something like "download limit exceeded, wait 1 hour".
so if you are not part of a private network that shares the same gateway, or, as lilrofl said, you use a shared poxy, there are only 2 possible reasons:
- error on the RS-side
- someone is abusing your connection
ok, another reason could be that your ISP is a VERY small one and another customer of that ISP used the IP right before you, then he disconnected, you connected and got the IP instead...but in this case RS should say something like "download limit exceeded, wait 1 hour".
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lockedin2code
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Multiple IPs on the Internet?
It's great to have replies!
I just attempted this again, and I'm getting exactly same message.
P/S:
The ISP has quite a large subnet
I wouldn't want to think they use NAT
RS making same mistake is almost out of the question
My connection being compromised such that SOMEONE ELSE USES my IP?
I just attempted this again, and I'm getting exactly same message.
P/S:
The ISP has quite a large subnet
I wouldn't want to think they use NAT
RS making same mistake is almost out of the question
My connection being compromised such that SOMEONE ELSE USES my IP?
We're bugs if we don't share knowledge! What have you got to give?
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bad_brain
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no, I meant NAT within your local network...when you use multiple computers that connect to the internet through the same router...
if you are the only host in your network it might be that your system is compromised.....but I doubt it's like "someone hacked the system". are you using a wireless connection? maybe one of your neighbors "felt free" to use your wireless access point too.
you could use Wireshark to check the traffic...simply let your system idle and look if something is going on (don't worry when there is a little traffic even when you do nothing, DNS- and broadcast-messages are normal, what I mean real traffic like downloads, surfing).
the WLAN NIC support in Wireshark is pretty limited, so in case it's not working you should also be able to see the connected hosts in the router administration.
if you are the only host in your network it might be that your system is compromised.....but I doubt it's like "someone hacked the system". are you using a wireless connection? maybe one of your neighbors "felt free" to use your wireless access point too.
you could use Wireshark to check the traffic...simply let your system idle and look if something is going on (don't worry when there is a little traffic even when you do nothing, DNS- and broadcast-messages are normal, what I mean real traffic like downloads, surfing).
the WLAN NIC support in Wireshark is pretty limited, so in case it's not working you should also be able to see the connected hosts in the router administration.
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lockedin2code
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Multiple IPs on the Internet?
Thanks! It's not wireless. It's 3G modem (HSDPA-based).
I think I finally got it! Looks like my ISP dynamically changes my IP every n secs - even without my reconnecting. From time to time, the IP just changes.
Going by your previous explanation, this implies that assuming another user had my 123.123.123.111 when he initiated his download on RS and my ISP gave me same IP some other n secs later, RS would assume that's me!
This explains why when I'm on some sites, my session is destroyed from time to time and I have to re-login. Probably the system assumes I'm not same person!
I think this is not security-safe!
Given to my thought, this could make SESSIONS that rely on USER IP ADDRESS vulnerable to session hacks.
EXPLAIN THIS and COMMENT, PLEASE...
I think I finally got it! Looks like my ISP dynamically changes my IP every n secs - even without my reconnecting. From time to time, the IP just changes.
Going by your previous explanation, this implies that assuming another user had my 123.123.123.111 when he initiated his download on RS and my ISP gave me same IP some other n secs later, RS would assume that's me!
This explains why when I'm on some sites, my session is destroyed from time to time and I have to re-login. Probably the system assumes I'm not same person!
I think this is not security-safe!
Given to my thought, this could make SESSIONS that rely on USER IP ADDRESS vulnerable to session hacks.
EXPLAIN THIS and COMMENT, PLEASE...
We're bugs if we don't share knowledge! What have you got to give?
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bad_brain
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ewww....best get a new ISP asap.. 
well, imo it's not a security risk, it's just annoying, because a session is only valid with a matching cookie (session ID), if someone gets the IP you have used a minute before he simply gets a new cookie (because he had none) which means it's a new session.
it would only be dangerous if the person would be able to retrieve your cookie, then your session could be hijacked.
well, imo it's not a security risk, it's just annoying, because a session is only valid with a matching cookie (session ID), if someone gets the IP you have used a minute before he simply gets a new cookie (because he had none) which means it's a new session.
it would only be dangerous if the person would be able to retrieve your cookie, then your session could be hijacked.