CAYMAN ISLANDS - Kellogg Brown & Root, the nation's top Iraq war contractor and until last year a subsidiary of Halliburton Corp., has avoided paying hundreds of millions of dollars in federal Medicare and Social Security taxes by hiring workers through shell companies based in this tropical tax haven.

The Defense Department has known since at least 2004 that KBR was avoiding taxes by declaring its American workers as employees of Cayman Islands shell companies, and officials said the move allowed KBR to perform the work more cheaply, saving Defense dollars.  Read more