Detecting SIM Swap in Telecom Core – Which API/Interface?

[huynit]

Hi everyone,

I’m building a solution to detect SIM swap (when an MSISDN becomes associated with a new IMSI) in a 4G/5G core network.

Right now we receive monitoring events (S6t) from HSS/SCEF with User-Identifier (MSISDN/IMSI). I want to know:

Which API/interface or data source should be used to reliably detect SIM swap in the core network?
For example:

S6t monitoring?

S6a/S6d?

Other core network APIs?

Should we track IMSI–MSISDN associations, ICCID, IMEI?

Any recommended interfaces or best practices?

Thanks! 🙏