1) You can generally trust network equipment because there are many types of it, produced by many companies all over the world.
2) This means any backdoor in your computer that transmits information over the network would be trivial to detect and therefore useless for NSA et al.
With that in mind, the most dangerous backdoor that could feasibly exist is probably the one that subverts the RNG. Here is a discussion about a hypothetical backdoor in the hardware RNG built into new Intel CPUs: http://crypto.stackexchange.com/questions/9210/technical-fea...
There'd be plenty of ways to use existing network traffic as a side channel when you've tapped the network a few hops away (eg adjusting packet timings or sequence numbers). Also, a backdoor doesn't have to be active all the time (although that would hinder dragnet surveillance)
This is the heuristics I use:
1) You can generally trust network equipment because there are many types of it, produced by many companies all over the world.
2) This means any backdoor in your computer that transmits information over the network would be trivial to detect and therefore useless for NSA et al.
With that in mind, the most dangerous backdoor that could feasibly exist is probably the one that subverts the RNG. Here is a discussion about a hypothetical backdoor in the hardware RNG built into new Intel CPUs: http://crypto.stackexchange.com/questions/9210/technical-fea...