Quoted from IMDB
As the humans begin to grow wary of the unwelcome intruders, a private company called Multi-National United (MNU) is assigned the task of controlling the aliens. But MNU is less interested in the aliens' welfare than attempting to understand how their weaponry works. Should they manage to make that breakthrough, they will receive tremendous profits to fund their research. Unfortunately, the highly advanced weaponry requires alien DNA in order to be activated. When MNU field operative Wikus van der Merwe (Sharlto Copley) is exposed to biotechnology that causes his DNA to mutate, the tensions between the aliens and the humans intensifies. Wikus is the key to unlocking the alien's technology, and he quickly becomes the most wanted man on the planet. Ostracized and isolated, Wikus retreats to District 9 in a desperate bid to shake his dogged pursuers.