Don Riley is an agent with the CIA.
It is important to point out here that the selection of Riley as the centerpiece of these exciting military/espionage adventures is mine and is admittedly open to argument. I give Riley that starring role because of how the sequence of events will lead to his playing what I consider the lead for most of the stories. He is not that at the beginning, though; that position will be filled by Brendan McHugh (more on him later).
I mention that Riley works for Langley. He will, eventually, a few years after we are introduced to him in the first recorded adventure. At that time, in 2003, he is a plebe at the U.S. Naval Academy trying the best he can to survive the seniors there and their constant downbeating of the newbies. He is sort of rescued, as it were, by two who befriended him and who will much later come back into his life, one of those being the aforementioned McHugh.
We next see Riley several years later as he was working as an analyst/field operative in war-torn Iraq in 2007. At that time we learn that an abdominal medical issue had racked his body in his sophomore year at Annapolis and ended his career in the Navy. But before any depression could set in, a representative from the Agency showed up at his door and offered him a different way to serve his country in its fight against terrorism.
From that start we will learn of his rapid advancement in authority as well as a shifting of employers (apparently). We watch as he moves over to the U.S. Cyber Command for a time before he is picked to head up the newly formed team inside the CIA's Operations Directorate called the Emerging Threats. "We get the stuff that falls between the cracks, the cases that don't fit neatly into anyone's portfolio. New terrorist groups, cyberattacks with no attribution, proliferation of WMDs, coups d'état, regional conflicts-if it's weird and new, we get first crack at it. And once we find the next threat, I'll have the authority to run field operations on that threat."
Riley, a red-head, is described as being around 5'8 and apparently prone to be a bit heavy, at least when we meet him but what more than made up for his physical issue, at least at the Academy, was his 'skills': "Riley consumed information like most people breathed air, and some claimed his computer skills were hacker level".
The adventures detailed in these books and shorter works showcase really an ensemble cast.
Leading that group is, as previously mention, Brendan McHugh, a U.S. SEAL who will rise to the rank of Captain in the Navy and becomes head of the CIA Trident program. McHugh is a natural leader and very much a man of action who would prefer to be out in the thick of things than lead from the backroom.
Also of considerable importance in nearly every adventure is Liz Soroush, a former Naval officer who joins the FBI after her required time in service. She would marry McHugh and while he was pursuing his career, she was advancing in the Bureau and will eventually become Assistant Director of the FBI's Counterterrorism Division.
Younger members of the cast would include Janet Everett, Andrea 'Dre' Ramirez, and whiz kid Michael Goodwin.