I have worked in telco and had to fix an issue with a circuit once, so ended up auditing the in/out circuits to which I found a few that were somewhat undocumen

I have worked in telco and had to fix an issue with a circuit once, so ended up auditing the in/out circuits to which I found a few that were somewhat undocumented and further enquiry was basicly, you do not touch those. reason for auditing was issue with video link and was looking for a spare circuit to negate a older bit of kit that I suspected of inducing the odd bit error. Which for networking is not going to be noticed but for video, visually impacting. This was about 20 years ago. Let us not forget that many a spare fiber was laid in the internet boom, unused and classed as dark fiber. But in government and telco's of the time and to this day you will find no single person working on the entire network to the stage they deal with there part and somebody else deals with there part. you can easily end up with unnoticed and ignored links for security. What I'd be interested in is what about Russia, China and other countries, so much about the NSA and yet more is known how they operate in contrast to other countries security collectives. But kinda gets down to presuming they see everything and with that, more right than not.