Do Internet Providers give the same IP for more than one customer?
I want to know if an ISP could give the same public IP address to more than one customer. Theoretically it is possible right?
If they can is it something they do regularly? I mean, not necessarily all the time, but I wonder if it's something that eventually happens
Me and my neighbor could be sharing the same IP to the internet?
My question actually comes from a security reason. To defend from DOS attackers I would ban their IPs for some time. Would other people get affected by that?
In a real production scenario, would you solve DOS by blocking IPs at application layer?
A public IP address is normally assigned to an internet connection. Typically that means an entire home or office or an individual mobile device. So you and your neighbor will typically (unless your neighbor is using your WiFi or vice versa) be on different IP addresses.
However, many ISPs will recycle IP addresses. This happens frequently on mobile devices as the IP address at any moment will typically be assigned based on the cell tower you are connecting to. With cable, DSL and fiber connections your IP address may be constant for days or even months at a time, even without having a contracted static IP address.
Where this really comes into play is blocking spam. Many spam filters depend in whole or in part on real-time blacklists (RBLs). I have also done similar things (aha! it IS a programming question!) to block spam robots from some customer web sites.
If an IP address is associated with a region of the world where you do not expect to have many customers (or to receive any email from that region) then it is generally safe to block a large range of IP addresses. On the other hand, if the IP address is local to your customer base then blocking a large range would not be advisable, and even blocking one known problem IP address at a time can be problematic if either the IP address is reused and then effectively unavailable to some other potential customer OR if the IP address is actually an email server used by a large group of customers (this happens frequently with hosting providers that don't manage blacklist issues).
(please redirect my question to relevant stack site, if I am in wrong place, however here I feel guaranteed to get help)
When playing with traceroute command I want to be sure I am not connecting to virtual host that may be dynamically mapped to a number of geographically dispersed servers(since it does not make much sense to track packets jumping from continents).
So more precisely with concrete example: how to prove with help of nslookup -querytype=NS google.com that google may redirect me to different servers across the world. I tried IPconfig locator for all values returned by nslookup, it always returns same location: California Mountain View.
It seems I don't understand something really important in here. Thanks.
update: tried nslook up from australian server, all the ip adresses still point to same location..
You cannot prove the location of any host. At the very best you can make an educated guess.
Geolocation databases are a big list of IP addresses and where the machines hosting those addresses are believed to be located. But they are just a guess and even the best of them are only 90% accurate to the state/regional level, meaning 10% of the addresses are someplace completely different. I use MaxMind because they have a fairly accurate free version and their commercial versions are not too expensive. They also have a free web-form where you can do 25 lookups per day.
You can use tools like traceroute to see some of the machines between you and your destination. Sometimes they have geographic locations in their DNS names. Sometimes their IP addresses will be listed in Geolocation databases. However, not all routers respond, many segments are virtualized and so their hops/routers are invisible, and firewalls may block the trace before it completes.
DNS databases list the address of the organization who owns an address or domain. DNS names themselves can be anything anyone wants, so even they contain geolocation information, there is no reason to believe it is true. In particular, a router might have a DNS name indicating the destination its connecting to, or even the administrative office responsible for it, and not the physical location of the device itself.
The IP address you are talking to can forward anything it wants to anywhere else it wants and there's absolutely no way you can detect that. So you can only follow the trail up to a point.
To make a good guess for the location of a host, look-up its IP address in a geolocation database, then run a traceroute and look-up the IP address of the last router before the destination. That will get you as close as you can.
This is more of a concept question than a code question, but I think someone will be able to explain it, anyhow.
I know that it is possible to blacklist/block an IP address from accessing a site, but how does this work if the user has a dynamic IP address? Wouldn't this mean that when the IP is renewed that user would be able to access the site under the new public IP?
Maybe I have the concept down wrong, but any information would be helpful.
Thanks!
If you are just wishing to block "nusisance users", as well as blocking their IP you could also place a Cookie on their machine to enforce the ban in their browser (then with each subsequent access attempt, block the new IP).
This, of course, would be fairly easy to circumvent, but ultimately there is no way for you to identify a visitor as they can very easily use a different connection, a different browser, or even a different physical device.
The best you can do is enforce bans against average nusisance visitors, and hope your website doesn't particularly attract that sort of person to begin with.
Yes that's what it means. It will be a different IP so you won't know that it's the same user. The only thing you can tell is that it is the same ISP. Which won't help you that much.
This is the exact reason that IP-blocking is easily circumvented. Even with you blocking all of their IPs, they could just use a proxy.
"Wouldn't this mean that when the IP is renewed that user would be able to access the site under the new public IP?"
Yes. Which is why when dynamically assigned IPs are blocked they're often blocked on a subnet basis rather than on an individual basis.
That also means that innocent parties get blacklisted.
Here is my situation. I am part of a project creating a P2P charity website, where users connect and can give money to one another. Because of the nature of the site, we know scammers are going to be rampant. We have several preventative measure ideas, and one idea that came up was tying an IP address to the user's account. The reason for this would be to be able to detect when someone from the same IP address creates several accounts.
Would this be reliable? Why, or why not? I have been googling and found many conflicting ideas on the subject. Thanks for any help you can give.
No, it is not reliable. Because:
Residential customers who aren't specifically paying for a static IP address will often see their addresses change frequently. I'm on AT&T DSL and I see my IP address change roughly twice per month on average
People legitimately sharing an internet connection, whether they're using different workstations in the same office with a T1 line, or they're all connected to the same Wi-fi hotspot at Starbucks, will all have the same IP address.
Related to the above, people who are mobile, such as people who use laptops to connect to Wi-fi at coffee shops, airports, hotels, etc, will have a different IP address for each location they visit.
Even people who stay in one place with a static IP address can spoof your system by using a proxy server or a proxy tool like Tor. This makes IP restrictions trivial to bypass.
No.
Many connections are behind NAT (One public gateway IP address for many people), or use DHCP (frequently changed IP addresses).
An IP address is one of the worst ways of identifying a user.
There is a dicussion board I am part of that bans sock puppets ( that is, multiple accounts by the same user ). They have no means of automatically detecting them, becasue there is no means of definitively identifying them. IP addresses are captured, because they can be used to help identify sock puppets, but I know that the process of identifying these is laborious, manual, and error-prone.
This is only undertaken when there is suspicion that someone is using sock puppets for malicious or disruptive purposes. In your case, there is no real answer other than careful and manual monitoring of usage habits, using the information that you gather about users to attempt to identify suspicious habits. But you also have to accept that 80% of sock puppets will go undetected, and do what you can to warn other users of the possibility.
Your bigger issue, incidentally, may be Munchausen by Internet which we were also caught by.
No, not least because:
IP Addresses can change over time, thanks to DHCP leases expiring.
People access websites from many different locations including home, work, coffee shops, etc.
When behind a NAT firewall or a proxy server, many people can share the same IP address.
Will you have many people registering who are entitled to receive money? I'd suggest a manual verification process using real people if at all possible. If nothing else, you can claim to be exercising due diligence if there's a human involved.
No: for example, any company proxy will only have one external IP address, so everyone registering from within the network will appear to have the same IP address.
Recent legal case perhaps worth reading up on : http://yro.slashdot.org/story/11/05/03/2020205/An-IP-Address-Does-Not-Point-To-a-Person-Judge-Rules
Totally unreliable...
Somebody on dial-up will have a different IP address every time they "dial-up".
DSL users will have a different IP address every time they reset or reconnect their account unless they pay for a static IP.
Many users on a particular LAN will be sharing one public IP address.
A particular user can login from home, work, public hotspot and have a different IP from each location.
I do development for an ASP service, and we have recently went through a required 3rd party security audit to obtain status allowing us to host data for a certain government agency. So if I may share some of the information I gleaned turning the trainings, perhaps it would help.
First, IP addresses can be used to assist in what you are trying to accomplish, but they are definately not good by themselves. An example would be the wireless at McDonalds. Everyone at McDonalds is connected to the same wireless and are using the same public IP address through a NAT, which translates from a local address (i.e. 192.168.0.xxx) to a public address for all computers located behind it. The NAT keeps entries so it knows what traffic is allowed to come back into the network, and which computer it is going to.
We found that a good security measure is to use an encrypted session key that is included with all GET/POST submits. That session key contains a GUID which is a lookup to the current session. So even if someone breaks your session encryption, they still need to guess at a GUID in order to find a valid session. On top of that, by tracking IP addresses, if it changes suddenly, we can immediately invalidate the session (we also have whitelisting in case someone is load balancing multiple internet lines, which can cause the IP to change frequently). A cookie can also be used in place of the IP address tracking, as two people behind the same NAT can potentially hijack each other if they can find a way to steal the other person's session key.
Encrypted cookies are also a good way to enforce security. But make sure you are using a framework that is tried and tested, as they have already closed the known vulnerabilities for you. Believe it or not, our security company told us that .NET has emerged as one of the top secure frameworks that they know of. I almost fell out of my chair when I heard that.
Personally I don't think it'll be reliable.
The main reason will be for those using a shared IP. That includes most users connecting from inside a business and home users connecting through the same WIFI hub.
It's more than likely for multiple users to be coming to your site with the same IP address.
Adding to that the fact that IP addresses change over time and you're already losing track of your users.
It's also worth remembering that oftentimes multiple users will be using the same physical computer. Are you wanting to have only one member of a household able to signup etc?
It could be somewhat useful as part of a defense-in-depth approach, but I wouldn't call it "reliable".
If you want to identify users, you can use a cookie. One solution uses a combination of cookies, local storage, flash, and other state information that can be stored in a browser: http://samy.pl/evercookie/
Nothing is 100% reliable. These cookies can be erased by a determined user, or in some browsers with one click. Ultimately, in many countries outside of the USA, a user has the right not to be tracked.
As an alternative for the future: New Intel® Business Processors Deliver Leading Security, Manageability and Performance
As long as the connection between the browser and the CPU isn't interviened which I believe there is more risk of with a browser than a desktop application.
Is it possible to know network card id of the user host computer from where the request is coming like IP address. I am interesting to know if it is possible at IIS or asp.net level or any other possible way of knowing it?
As far as getting network card information is concerned, I see little hope for you here seeing as a client's hardware profile is not something naturally pushed down the wire as a matter of course, however see:
HttpContext.Current.Request.UserHostAddress
Or
HttpContext.Current.Request.ServerVariables("remote_addr")
This value will give you the IP address of the calling client, although they may be hitting you through a proxy and therefore can't be guaranteed to be a machine specific address.
If by "network card ID" you mean the Ethernet MAC address, that's assuming a particular technology on the remote side that you have no way of knowing whether or not it is used. Sure, Ethernet is used pretty much everywhere these days, but are you willing to limit yourself to clients that use that particular hardware architecture? So even if it were possible, I doubt you'd want to go down that route.
If what you want is a unique identifier per client computer, you are probably better off issuing some sort of token yourself. A cookie with a randomly generated session ID should work fairly well.