Comment by blauditore

> But is very easy to bypass, and I won't tell you how.

That really depends on how it works, and whether you know how it works. Simple signals such as IP location and temporal distribution of votes are easy to use for detection, but also easy to manipulate. On the other hand, if you employ a graph of user associations based on votes and comments in the past, you can detect clusters among them, voting collaboratively. This is way harder to circumvent in the long run, but also extremely difficult to implement accurately.