I get messages everyday in Telegram.
Most of them approached me as investors, group admins or affiliates.
One way to detect them is that they will approach us first. And they always start with 'Hey User'.
Real investors or admins dont simply approach other people until we ask for their help first.
I can't really say I was scammed personally because I was involved in a bigger deal but I basically lost money twice in a communal way.
First one, was cryptsy which was one of the early multi coin exchange in crypto world, think of it like today binance or bittrex. I had some money there and when they claimed they were "hacked" they just took our money and left, I can't say I was scammed because they basically took everyone money and didn't really aimed me about it but thats still money lost for me.
Second one was hashflare where I have spent money to get hashing power but in the end they claimed it wasn't profitable anymore and closed shop and I never got my money back from them neither. All of them together I have probably lost about one bitcoin in them but right now not much I can do about any of them.