Good question. SMS are transmitted over the NAS layer of the 3GPP stack, which terminates beyond the cell (NB/eNB). There is NAS level security but I don't know

Good question. SMS are transmitted over the NAS layer of the 3GPP stack, which terminates beyond the cell (NB/eNB). There is NAS level security but I don't know if it's end-to-end or only over the air link. Hopefully it's the former but one should dig the specs at 3gpp.org to confirm.