I have a product and we are running a campaign for it to allow users to download a trial version. My questions is there any way to detect multiple downloads from the same computer but behind a proxy.

For example if a person uses a proxy server, changes his/her ip and downloads our trial version multiple times from different Ip's, is there a way to detect that it is the same person who's downloading the s/w. We use only Name and Email addresses to be entered before downloading our s/w and that can easily be created. We cannot add any other fields to the form (like phoneno.)

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    Are you storing a cookie in their browser? Other than that, there is no real way for you to do what you are looking for. The better question is, once they have downloaded it once, why can't they make as many copies as they want? – soandos Jun 12 '12 at 2:59
  • I think you should have to use some kind of hardware ID and then check out it. In this way you can track down easily the system. After trial version period if user try to install it again then it should check that ID and previous installation and refuses the setup. AS Internet download manger do. – avirk Jun 12 '12 at 3:18
  • adding to avirk: One of the hardware IDs that you can check is MAC address – tumchaaditya Jun 12 '12 at 4:35
  • let's assume a user has downloaded the product but not installed it. Can I still get is MAC address? – CuriousDev Jun 12 '12 at 6:29
  • soandos Every time a trial is downloaded, we pay a certain fees to the vendor. Hence we have to track if the same user is not d/l using different ip's behind a proxy – CuriousDev Jun 12 '12 at 6:30

You could hand out and track cookies (but then the user could simply delete those, if they notice).

You could also compare browser id strings and so forth.

You could also try something like the CSS history hack to identify whether the user's browser thinks that they have seen a certain page/page element before, or downloaded a certain image from the page before (but that type of approach would generally fail if the user had JavaScript switched off, had a smart browser, used NoScript, had a whitelist, etc).

Probably easier to work within the assumption that users may be repeat 'customers', and leave it be at that.

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