EDIT: Ah, it's from Gamespot.
There's nothing official from SEGA, but it looks like this might be the new trailer for Gearbox’s Aliens: Colonial Marines, below. It has come skittering out of the darkness on YouTube, but there's a good chance SEGA will set the flamethrowers on it if this is a leak.
Regarding the trailer itself, there’s plenty of frantic shooting and yelling but the edit builds up the tension and horror as well. It’s the first time I’ve seen enough of the game to shift from mild anticipation to fervent excitement. Some moments look scripted but they appear to be scares rather than action sequences. If the game can balance the gungho of Aliens with the dread of the first film, it should be a winner.