What is a HECM? | Ginnie Mae's HECM Loans and HMBS Securities – HECM loans are pooled into HECM mortgage-backed securities (HMBS) within the Ginnie Mae II MBS program. HMBS are made up of a pool of participations in the HECM loans. A participation in a HECM loan is a pro-rata share of the loan that is securitized in a HMBS.