The "root of all evil" has been discovered by scientists who found that part of the brain fires up before nefarious acts are carried out.
Researchers wanted to find out if bad intentions could be seen forming in the brain before any violence or aggression took place. They found that a distinct part of the hypothalamus - the brain region that controls body temperature, hunger and sleep - is activated shortly before an attack.
The study authors, from New York University, say it may be possible to spot warning signs of premeditated violence, stalking, bullying and even sexual aggression, and prevent it occurring for good.
"Our study pinpoints the brain circuits essential to the aggressive motivations that build up as animals prepare to attack," said Dr Dayu Lin, of the Neuroscience Institute at NYU Langone.
The part of the brain that switches on before aggressive behaviour is known anatomically as the ventro-lateral part of the ventromedial hypothalamus, or VMHvl, because of its central location inside the brain on the underside of the hypothalamus.