Overview#
Signalling System No. 7 (
SS7) is a set of
Telecommunications signaling
protocols developed in
1975, which is used to set up and tear down most of the world's
Public Switched Telephone Network (
PSTN) telephone calls.
Signalling System No. 7 is part of the common-channel signaling (CCS)
Signalling System No. 7 also performs number translation, Local number portability, prepaid billing, Short Message Service (SMS), and other mass market services.
Common Channel Signalling System 7 (CCSS7) is how Signalling System No. 7 is referred to in the United States and In the United Kingdom, it is called C7 (CCITT number 7),
What does Signalling System No. 7 do?#
Signalling System No. 7 is a set of
protocols allowing phone networks to exchange the information needed for routing
data between each other and to ensure correct billing.
Signalling System No. 7 also allows users on one network to roam on another, such as when travelling in a foreign country.
Edward Snowden’s
2013 document dump revealed that the
National Security Agency was using Signalling System No. 7 for
Surveillance on
individuals.
There have been several SS7 hacks.
There might be more information for this subject on one of the following: