Subversive (noun)-  A cause of overthrow or destruction.
The content in which the word is being used is, “People are beginning to exercise a bit more reverse online or are otherwise engaging in subversive tactics to thwart data miners.”
Article: “We Want Privacy, but Can’t Stop Sharing,” by New York Times.
The definition that merriam-webster.com in other words state that the word subversive is being overthrow or destruction. The writer is explaining to us that sometimes we have to stop doing things that we may like doing to help us reap the benefits.