Well who on earth do you think you are interfering with the aircraft like this. How do you think the crew feel when they see you (a passenger) fiddling around with the FD door? The sock serves a purpose- to stop the (unlocked) FD door banging right next to the bunk unit. Quite simply the sock has no relevance to FD security and it is non of your business! If you have an issue about the philosophy of LOCKING the door, that is another matter. The BA view is that any malicious intruder can quite simply gain access anyway. It is Cabin Crew involvement that can stop it. I concur with this as a 747 pilot of 16 years.