Which of these covert groups employs Sam Fisher to work as a Splinter Cell?

The covert group that employs Sam Fisher to work as a Splinter Cell is Third Echelon. This top-secret unit is part of the National Security Agency (NSA) and is responsible for conducting covert operations and gathering intelligence. Third Echelon recruits highly skilled operatives, like Sam Fisher, to carry out sensitive missions with precision and efficiency, blending in with the shadows and using stealth tactics to accomplish their objectives. Sam Fisher's training and expertise make him an invaluable asset to Third Echelon, as he has proven himself time and again as one of the best Splinter Cells to ever work for the group.