This may be one of the trickiest scams in the book. It is notoriously hard to detect.
The reason for this is that many cloud mining websites are actually genuine.
Cloud mining involves the pooling of monetary resources in order to rent a rig which would then mine Bitcoins. In legit operations, this setup works entirely and you would be able to generate decent returns.
These scam websites appear and pretend to be an investment vehicle for mining cryptocurrency and then simply disappear with your money once you get suspicious.
Many of them get harder and harder to detect...but by sharing information between us users we can spread what we learned and maybe keep clear of them.