[quote=eddieddi]
They all feed in to the main system. thats the glory of a feedback loop, it moves up the chain of command, infect the lowest stage and it'll work its way up.
[/quote]

There's no comunication from top to bottom, meaning that you'd get up to the main console, but you'd only get the subroutine you had hacked into. Furthermore, you'll still need an access point to even affect the system. Lastly, if you were to cause all the cameras to play a 1-second loop, someone's going to notice.