[VOIPSEC] VoIP Attack : How feasible

[Gupta, Sachin]

I have a very basic question here.
How easy or feasible it is to launch any kind of attack on internet , be
it VoIP or anything else? Apart from the insider attack, how would
somebody be able to read the data that i sent on wire.
I can understand that such attacks are possible in an enterprise
scenario, but do not understand the scenario in which somebody could
launch these attacks over the internet.
Can somebody provide some information here
 
Thanks
Sachin