A police subdepartment responsible for neutralizing anti-government activities in pre-1917 Russia was called, in colloquial speech, okhranka (from okhrannoye otdelenie, “protection unit”), NOT *okhrana. The -k- suffix conveys familiarity and/or disparagement, and is common in colloquial Russian abridgements (sluzhebka from sluzhebnaya zapiska, a sort of office memo, platyozhka from platyozhnoye poruchenie, payment order). Okhrana is quite a respectable word: the US Secret Service is, in fact, the President’s okhrana, and protection of the environment is okhrana okruzhayuschey sredy.
I’ve run across this mistake a thousand times, most recently while reading Christopher Hitchens’ piece on Victor Serge. It must have sprung from a misprint in a well-respected source.