The BGP Problem
The attacks on the Bitcoin blockchain are non-stop 24-7. Aviv Zohar and his colleagues at The Hebrew University, Israel have shown where to attack the Bitcoin cryptocurrency via its internet routing mechanism that it uses.
The Bitcoin devs have a problem, as they don't have a mechanism to protect the vector into the BGP (Border Gateway Protocol) that tell IP packets how they are routed across the backbone of the IP network.
Having worked in IT and telecoms myself, I know that BGP's problems are well documented. This was a protocol formulated in peaceful times before the arrival of cryptocurrency. It does for example trust the information is receives without questioning it whether it's from a rogue source or not??
If a wayward ISP suddenly decides to send incorrect BGP data into the network, then it's possible to 'black hole off' some of the internet traffic.
This full on attack would be a rude wakeup call because it would be completely undetectable. It's a well know fact that 50-60% of all the Bitcoin nodes reside with just 3-4 ISPs. Thus the probability of damage by a rogue employee is immense.
The big telcos know this and work hard to maintain the highest integrity of their staff but as we all know, if it can be man made, it can be man broken. This is indeed Bitcoins weakest link if there is such a thing.