What was done by the underground and others to combat the Nazi’s most commonly was called mental reservation.
An example of mental reservation is…
A salesman comes to the door and asks if your mother is home. Mom is in the kitchen and does not want to or does not have the time to see the salesman. You reply, “No my mother is not home” on the outset it sounds like a lie, but if you in telling him that you are not sharing that “while she is in the house, she is not here for salesmen at this time” you are reserving that information which he does not need to know in order for your mother to conduct the business she needs to attend to without interruption.
With the Nazi’s if they asked, “Are there any Jew’s (or other people that the Nazi’s wished to immorally persecute) here?” one could answer honestly, “No, there are no jews here (reserving mentally, for you, or that you should know about.)
Another example was a Seminary in Rome during WWII. The Nazi’s heard that jews where being harbored there. The commander of the Nazi’s in Rome came in with his men and asked if there where any jews in being hidden in the seminary, the rector replied, “No” The commander pointed at a man in a cassock, (a jew who was being “hidden” in the open) and asked “Who is that man, is he a jew?” the rector replied, “Oh him, he is our Old Testament Scholar.” He only answered what the Nazi needed to know and stopped before he endangered the life of the jew. He did not lie to the Nazi, he simply reserved some of the information that the Nazi had no honest reason to have knowledge about.