The author, using the literature on the subject and archival sources, indicates the most important issues related to the security of underground work during the Second World War of the ZWZ-AK. It does not only focus on describing the structures and operation of counterintelligence, which is mostly the focus of researchers of the subject, but also deals with the guidelines for the service of a single soldier and their implementation by underground soldiers. An important part of the article is an indication of the still not fully clarified question of the great influence of the ZWZ-AK counterintelligence on the orders and instructions on the rules of underground conduct appearing in the underground.