Trump only mentioned the name of one of the four he's considering — retired Lt. Gen. Keith Kellogg.
Kellogg served 36 years in the U.S. Army and was director of the Command, Control, Communications, and Computers Directorate under the Joint Chiefs of Staff.
Other names floating around for the position are retired Gen. David Petraeus, retired Gen. James Jones and retired Gen. Keith Alexander.
Petraeus was director of the CIA for just over a year under President Obama. He served as the top U.S. commander in Iraq under President Bush. Petraeus is currently serving probation for sharing classified information with his biographer, with whom he also had an affair.
And former ambassador to the United Nations John Bolton could be a dark horse candidate for the role. Sen. Ted Cruz told CNN on Friday he'd like to see Bolton in the position.