REAL solution against "multiple times" poll voters

Using the cookie thing?

That's a solution to work against only those who have no idea how to use there PC-s.
Anyone else just cleans the cookies and cache, and by doing this they can vote 100 times in the same poll if they wish.

Having the IP table set to on?

This and with the "lockout time" set to some time again won't work, because people can find tens of free online proxies to use, and with each proxy they can vote once.

As conclusion

Is impossible to find a real way against those who want to vote for multiple time, and by this to alter the unbiased result of a poll.

I still have my cookies on, and the IP check on, with the same lockout time like the cookie time, because these 2 combined still give a little more defense against multiple voters.

Any ideas how to defend better against multiple voters?