This excerpt taken from the STT 10-K filed Feb 27, 2009.
Mortgage-Backed Securities Purchase Program
The program, announced by the U.S. Treasury in September 2008, is designed to broaden access to mortgage funding for current and prospective homeowners, as well as to promote market stability through the Treasurys purchase of new mortgage-backed securities issued by Fannie Mae and Freddie Mac. The program is intended to expire on December 31, 2009. In October 2008, SSgA was one of two asset managers appointed as an agent to manage assets purchased under the program.