Pretty much all DRM content has unique patterns.
Want to prohibit videos of the Starcraft game? Simple search for a few sentences like "more vespene gas" and "require more minerals".
Want to find online copies of "Aliens"? Just enter a few catchphrases or part of a dialogue like "They come mostly at night. Mostly."
And even then, you can't filter conversations in real-time, only maybe 'flag' people with forbidden words.
Yes, that's really assuring to know it's not in real time.