A security log is a record kept by the chief of security of a starship or starbase.
Several log entries were made in the security log aboard Deep Space 9, as recorded by Constable Odo. (DS9: "Necessary Evil")
In 2370, Kellerun and T'Lani authorities provided a data clip to Starfleet, of the security log of the laboratory where Miles O'Brien and Julian Bashir were thought to have been killed. (DS9: "Armageddon Game").
In 2371, when a young Jem'Hadar wished to know more about his people, Odo called up a bridge security log for the USS Defiant that showed the Jem'Hadar's boarding the vessel and attacking. (DS9: "The Abandoned")
Numerous log entries were made in the security log for the USS Voyager. They were recorded by Lieutenant Tuvok. (VOY: "Learning Curve")