These CDOs are identical to regular CDOs except for the assets securing the obligation. Unlike a CDO, which is backed by a pool of bonds, loans, and other credit instruments, CDO-cubeds are backed by CDO-squared tranches. CDO-cubeds allow the banks to resell the credit risk that they have taken once again by repackaging their CDO-squareds.
CDO-squareds and CDO-cubeds can be repackaged countless times to create derivatives that are quite different from the original underlying debt security. These are also referred to as CDO^n to show the unknown depth of some of these securities.