The US authorities have studied online sexual activity and suggested exposing porn site visits as a way to discredit people who spread radical views.
It published a document, leaked by former National Security Agency contractor Edward Snowden, identifying two Muslims said to be vulnerable to accusations of "online promiscuity".
An official said this was unsurprising.
But campaign group Privacy International called it "frightening".
I'm sure the NSA knows about every fetish and sexual activity of every member of Congress and all US politicians