Drenna Steel is an agent for the CIA.
More accurately, and far more importantly, she is an assassin for the Agency. She is a very good, and thus very dangerous, operative, as shown by the thoughts of a man determined to kill her in the opening pages of the first recorded adventure:
"The man had heard whispers about the woman's existence for years. She was the most sought-after spy in the world, a cold-blooded killer wanted by governments, terrorist organizations, and criminal enterprises around the globe. She was said to have eliminated at least two dozen high-value targets in the last five years alone. But it wasn't just the number of kills that gave the woman such a frightening reputation-it was her ability to find and take out people who thought they were well protected. No one was beyond her reach, it seemed.
"Over the years, many were convinced that the female assassin worked for the CIA, since her kills and information theft always seemed to benefit the United States or her allies. But others held different opinions. Some, for example, believed she worked for Mossad. In a way, that made sense because Israel's geopolitical goals often aligned with those of the US. Others claimed she was an independent contractor, an assassin who took work from any government or organization as long as the price was right.
"There were even a few intelligence analysts who believed she didn't exist at all. According to them, the killings were unrelated, and tales of a shadowy female assassin were unsubstantiated myth.
"But the woman did exist, and her identity was no longer a mystery to the man watching the cabin. She was a real person, she worked for the CIA, and she was about to die."
That would-be assassin does not succeed in his endeavor to remove Steel from living but he does provide the inadvertent impetus to stop her planned retirement from the CIA and keep a very, very deadly killer in the game, shown by the title of that adventure: "Retribution".