http://www.washingtonpost.com/blogs/the-switch/wp/2014/12/18/german-researchers-discover-a-flaw-that-could-let-anyone-listen-to-your-cell-calls-and-read-your-texts/
I don't know SS7 from a grilled cheese sandwich, so...but it is obvious stuff is ridiculously easy to hack for those with a modicum of ability!
I know SS7 and
1) Its not used in Cell Phone network Signalling. (there are a number of competing standards..) - it would only come into play when calls are sent to the regular PSTN
2) Its is run on point to point links with physical security - you would need a trusted link into the network before you could do serious damage
3) since its Signalling, you can't just "listen to a call" You would have to convince a huge network of Tandems ( PSTN speak for "router" ) to send the call to some intermediate point for surveillance and then get that same network of tandem to accept the call back into the network and route it appropriately. Its just not all that simple..
4) Monitoring a ss7 Link will let you know who called who and give you a pretty good idea of that path that voice call will take. Actually slapping a line unit on that trunk at that time is more difficult
5) SS7 was engineered deliberately to allow surveillance by the govt under warrant (CALEA) , so yeah, if you use that process you can listen to a call.
6) Who the hell uses SS7 anymore? 50% of all voice traffic is carried over SIP trunks which are in fact FAR MORE vulnerable to surveillance. I support a product that does that in fact.
7) don't want someone listening? - encrypt your voice path.
