USF's new Defensive Coordinator Tom Allen came from Ole Miss, where he was the Linebackers Coach and Special Teams Coordinator. The Rebels' 4-2-5 scheme was the best regular season defense in the country last year, and carried the team to a #3 ranking for a few weeks. Then they lost a few games and finally got blown out 42-3 by TCU in the Peach Bowl. Coincidentally, the Horned Frogs also do the 4-2-5.
The increased use of the 4-2-5 has grown out of the need to match up against spread offenses, and it is philosophically similar to the spread.