The Section is an ultra secret division of Säpo that harbored and protected Zalachenko. It is also the title of the book that Blomkist releases at the end of the trilogy, an expose on the secret division.
Evert Gullberg is the founder and former chief. Section associate Frederik Clinton becomes acting head of the Section and plots to deflect attention away from the Section by silencing Salander, Blomkvist and Zalachenko. It's members include Dr. Peter Teleborian.
The Section was created in 1964 and was referred to as "the last line of defense" for national security. It was never referred to in writing and was therefor invisible and unacountable. Blomkvist calls the Section "the Zalachenko club" at first, because it seems devoted to the protection of Zalachenko and his secrets. The Section has, in fact, been protecting him for decades and is largely responsible for Salander being committed to a psychiatric institution and deemed incompetent.
The Girl Who Kicked the Hornets' NestEdit
Gullberg, terminally ill with cancer, murders Zalachenko in his hospital bed and then commits suicide. Section operatives stage a suicide for Gunnar Bjorck, the junior Sapo officer who had handled Zalachenko after the latter's defection, and who was Blomkvist's source of information about the Section. Other Section operatives burglarize Blomkvist's apartment, mug Annika Giannini, and plant bugs in the homes and phones of Millennium staff. Undeterred, Blomkvist continues to investigate the Section for a Millennium expose. Gullberg leaves behind Fredrik Clinton, Hans Von Rottinger, Georg Nyström, and several other members of the Section, most of whom are arrested during Salander's trial.