Black Propaganda is, um, "false information and material that purports to be from a source on one side of a conflict, but is actually from the opposing side. It is typically used to vilify, embarrass or misrepresent the enemy." Obviously, this is still pretty relevant today: arguably, certain media narratives are basically a form of black propaganda, along with various Government announcements and 'leaked' stories.
The Germans were well ahead of the British on this at the start of WW2, but we caught them up somewhere around '42 and eventually surpassed them, setting up radio-stations that pretended to be part of the German Resistance movement, along with ones that broadcast Jazz and Porn (!!??) interspersed with disinformation bursts. Since the author is of Polish descent, the book also focuses on black propaganda before and during the occupation of Poland.
At one point there were 200+ black.prop radio-stations operating in Europe alone, each pretending to be something other than they were.