Bumping a thread will get you an infraction or even a suspension here at DP. Please do not bump threads. As for your question - you can't stop someone from changing their IP Address. IP Addresses are assigned by the Internet Service Provider in accordance with the terms and contracts you have signed with them (ie: Static IP versus Dynamic IP). While those that have a Static can still change it, those with Dynamic have no control over this what so ever. The only thing you can do is store a cookie on that persons browser and check if the cookie exists. Problem there is people know how to clear cookies, or delete specific cookies and not only that - many people have multiple browsers on their computer so if a cookie is stored in own browser, another browser will still be allowed. Unfortunately, unless someone else here has an idea that I haven't thought of - there is nothing you can do to prevent people from changing IP addresses.
Interesting question - from which point of view, network or affiliate? As an affiliate this will only happen if you incentivize offers, especially those that are not supposed to be incentivized. Which is bad regardless how you look at it. Maybe use a system based on flash cookies to track them when using the same browser, but the length to which you are willing to go will be easily matched by them if the incentive is too large (certain pay-per-download filehosting websites have this problem). As a network, just improve your scrubbing and refuse submissions through proxy. Exchange IP blacklists with other networks and measure conversions on sales or at least 2nd page submits. This is the main reason things become increasingly difficult lately with CPA - too easy to fraud the merchants / networks. @nyxano maybe you did not realize that the OP's post count was 2 at the moment he opened this thread. Affiliate Managers do this alot, but if they need to ask such a question, well.... no offense, but I would not worry too much.
ok I didnt know that I just read the rules. Its seems odd because i received more answers because of the bump. w/e thanks for the responses