jsp get ip address

Question

whats the best way of preventing someone from voting twice? How do i get the users ip address? What if they are on a large network? will everyone on that network show the sa

Answer 1

AFAIK the ONLY way of preventing a second vote is by authenticating. Obviously this is not always possible, so you have to mitigate the possibility of a single user casting a ton of votes.

• Throttle the voting by source IP. Use the getRemoteAddr() to allow, say... a vote per hour?... per minute? ... it will depend on how much voting you expect. Adjust the number according to experience.
• Plant a cookie on the response for every voting poll, which expires after the ballot closes.
• Make it harder to forge requests by checking and validating headers like Referer and User-Agent.