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.
There a lot of unknown groups and people that will add you and pm you in telegram ang you can easily tell if he/she is a scammer because they will convince you to invest your money with them. But mostly people got scammed in bounty campaigns and ICO project, and that is one of the reason why many people started to hate ICO projects.