Debt securities (such as bonds or notes) that are issued in the course of a securitisation and backed, (that is, funded) by and secured over a portfolio of cash flow-generating assets such as credit card receivables, trade receivables, auto loans and leases (though generally not mortgage loans as these are more commonly referred to as mortgage-backed securities). The underlying assets are pledged to the holders of the securities (often via a security trustee) as collateral for the payment by the issuer of principal and interest on the securities. Asset-backed securities are most commonly issued by a special purpose vehicle as part of a securitisation or structured finance transaction.