It used to be said of West Drayton, that there was a manhole in the street outside; where a single hand grenade would cripple the UK ATC network for a month.
Seems now a geek with a laptop in his bedroom could completely screw up the system with a couple of keystrokes.
Not to mention a foreign power with malicious intent.
The fancier they make the plumbing, the easier it is to stop up the drain
Mr Scott - USS Enterprise