How do you avoid ponzi schemes

[Nomad]

A lot of people who are trying to invest online fall into ponzi scheme. Ponzi schemes are structured as pyramids. Only those who are at the top of the pyramid profit whereas those at the bottom lose. Unlike gambling, where there is at least some chances of winning, on ponzi scheme you only lose money. Those who make money from ponzi scheme are only those who created these programs or the early investors.

When it comes to investing online, how do you avoid ponzi scheme?