This question references S2E12 ("Army of Ghosts") and S2E13 ("Doomsday") of the modern series.
Refresher - the Torchwood institute is allowing 'ghosts' through a rift in dimensions they discovered. These ghosts stand around wavering, entrenching themselves in family life, like the long invasion in S8E4 (black cubes, the doctor stays for a year, weird nurses with cubes in their faces). The people assume these ghosts are humans, but it turns out they are cybermen, coming through the parallel dimension visited in season 2 episodes 5 and 6 ("Rise of the Cybermen" and "Age of Steel", respectively). For reference, here's a ghost:
and here's what it becomes:
People around the world all assume these are the ghosts of their loved ones, partially due to intense belief that they are, and partially because that is propagated in the media. It's a good assumption too- the ghosts move organically, not mechanically by any stretch of the imagination. They don't even get into formation (as cybermen are so wont to do) until they are almost fully through. I get the flickering, but what's with the walking around? Why aren't the cybermen moving mechanically?