There's another phrase lurking just beyond recall, but this one is quite common. For instance, there was the case, a few years back in San Francisco, of the respectable-sounding Golden Gate Foundation, which was a front for a rather posh prostitution ring.

"Shell company" or "shell corporation" are other possibilities, as is "dummy corporation" -- all of which are intended to conceal their true ownership and/or purpose.

Cheers,
Heather