Considering the way he said it, or actually didn't say anything all, it is of course a given that this detail about his character is not supposed to be out in the open yet. If you would rather not know what was revealed, then turn back now.
Fassbender said that the "script is really intelligent and has a nice pace to it." Asked again about the film's connection to Alien, he added, "It's a different story, but it's also got the traditional roots. Alien fans will recognize things in it. It's not ignoring Alien, there's still a link to that world. But it's a different story. It's definitely connected, though."
And then he was asked whether he'll be playing an android in the film, at which time he laughed and said, "I don't know what I can say!" While he said that, he looked down at the reporter's tape recorder and then nodded affirmatively.
Prometheus is scheduled to hit theaters on June 8, 2012.