Dr. Martin Harris: They had me convinced that I was crazy. But when they came to take me, I knew.
The password needed to access Leo Bressler's hard drive, Umbellularia californica, is visible in the book. In the next shot 'umbellularia' is incorrectly typed into the password box as 'umbellurlaria', yet it gains access to the drive.
Throughout the movie if you look in the background at the various graffiti tags, one in particular stands out. Look for the tag OZ. In almost every scene that has graffiti on the walls you 'll see it somewhere in the background, sometimes more than once. Although it is common for graffiti artists to leave multiple marks in multiple areas, Berlin is a big city and it can be spotted too often for it to be coincidence.