at wikio.com, you can vote anonymously, how do you think they are doing this...?
- if I vote in FF, then clear cookies, it remembers I voted - if I then vote in IE, it still remembers I voted...
so it must be server side, but checking source IP would not be very good...
never mind, I just tried from my wifes machine, it still thinks I have already voted, so must be source IP
The IP address is provided to you by your web server which gets it from the TCP/IP connection between the client and the server. The three-way handshake makes it impossible to spoof the IP address, so this scheme works to ensure no dupes, but it causes problems if you share a connection behind NAT. If someone on your shared connection votes before you do, you're SOL.
In your rails controllers, you can get the IP via request.remote_ip.
CAPTCHAs, or requiring logins that are email verified... There are a number of solutions; they all have their pros and cons and which one is right for you depends on your app...
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