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SS7 is not fixable in my opinion. It needs to undergo the metaphorical equivalent of being burnt to the ground and having its ashes stomped around on a bit. Th

SS7 is not fixable in my opinion. It needs to undergo the metaphorical equivalent of being burnt to the ground and having its ashes stomped around on a bit. The further you go into the architecture of the "trust based" PSTN, SS7, traditional Telco stuff... The more you will see the total lack of modern cryptography, PKIs, zero trust network modeling, etc. I'll admit that my perspective is skewed by working in backbone IP network engineering for a mid sized ISP. We occasionally have reason to interact with some pstn related stuff. All of the real technical innovation, security advances and such have been taking place in the ISP world for the past 25 years, not the Telco world.

g_p 6y ago
Indeed, SS7 is based on a whole host of assumptions that just can't be relied upon. Since SS7 doesn't even bother to try to verify who anyone is (you'd only peer with trustworthy people, right?!), it's also very hard to hold anyone accountable too. And since the idea of SS7 signalling is that it can be forwarded and passed around, it simply needs to be replaced by authenticated, access-control validated signalling. Then you can at least have some confidence you're actually hearing from a network that has a reason to be communicating. Too much of SS7 comes from a world where anyone can do anything - there's no legitimate reason in 2021 for an arbitrary network to be able to request a user's network location and cell ID, but the protocols support it. SS7 firewalls try to plug the gaps, but ultimately you just innovate in how you try to get the network to hand over what you want, and eventually you'll find a way the firewall doesn't spot. Cat and mouse continues. Telco networks are "zero trust", just not in the right way(!)
amaccuish 6y ago
> The more you will see the total lack of modern cryptography, PKIs.. Funny you say that as x509 was an ITU standard. But yes, PSTN is terribly broken, with mobile bolted on.

g_p 6y ago

Indeed, SS7 is based on a whole host of assumptions that just can't be relied upon. Since SS7 doesn't even bother to try to verify who anyone is (you'd only peer with trustworthy people, right?!), it's also very hard to hold anyone accountable too. And since the idea of SS7 signalling is that it can be forwarded and passed around, it simply needs to be replaced by authenticated, access-control validated signalling. Then you can at least have some confidence you're actually hearing from a network that has a reason to be communicating. Too much of SS7 comes from a world where anyone can do anything - there's no legitimate reason in 2021 for an arbitrary network to be able to request a user's network location and cell ID, but the protocols support it. SS7 firewalls try to plug the gaps, but ultimately you just innovate in how you try to get the network to hand over what you want, and eventually you'll find a way the firewall doesn't spot. Cat and mouse continues. Telco networks are "zero trust", just not in the right way(!)

amaccuish 6y ago

> The more you will see the total lack of modern cryptography, PKIs.. Funny you say that as x509 was an ITU standard. But yes, PSTN is terribly broken, with mobile bolted on.