Read DR Jacques Vallee (as well as his buddy--name escapes me--PhD immersed in the black ops field concerning such for decades--Oh, yeah--Dr Hynek.) Both ended up essentially concluding that the critters do not come from distant orbs. And, that, essentially, they are evil spiritual entities coming from a dark spiritual DIMENSION.
Both of them probably know more about the critters than 10 randomly picked other experts combined.