What is SSI in kyc?

Could you please elaborate on what SSI stands for in the context of KYC, and how it plays a role in ensuring compliance with regulations? I understand that KYC is a crucial process for verifying the identity of clients, but I'm curious about how SSI specifically contributes to this process. Is it a technology, a framework, or a set of guidelines? How does it help in preventing money laundering, terrorist financing, and other illegal activities? I'd appreciate a clear and concise explanation.