CCTV catches busy ghost

The following footage was from a CCTV camera taken on the 9th of February 2007.  The ghost does not appear in a human form but more of a blotch of dark mass.  It keeps drifting around the left and bottom of the CCTV but doesn’t go to the other side of the hall.  A security guard can be seen walking towards the lift, the ghost then disappear  but as soon as the security enters to lift the ghosts comes out again and goes about it’s business.