Four hostile alien civilisations could launch attacks on Earth.

Four alien civilisations could attack Earth

Four alien civilisations could attack Earth

Space researcher Alberto Caballero has calculated the chances of evil extraterrestrials targeting the planet and has concluded that there could be four "malicious" alien civilisations.

Caballero studied human "invasions" of other countries over the past 50 years and applied that data to the number of known 'exoplanets' in the galaxy - which Italian scientist Claudio Maccone estimates to be around 15,785.

The cosmic expert said: "I did a paper based only on life as we know it. An extraterrestrial civilisation may have a brain with a different chemical composition and they might not have our empathy or they might not have psychopathological behaviours."

Caballero insists that the chances of an attack are small but says they have been increased by humans trying to make contact with alien life.