Violent extremism is a ideological disease that spreads in the same way as a infection through society.
 Violent extremism is not a "virus" at all. It's a product of poverty and lack of education, making the masses exploitable by unscrupulous individuals who seek quick wealth and power. Educate your people and extremism disappears. Do you think it's because of the TSA and the DHS that the US suffers relatively little "terrorism" (both before and after 9/11)?
As for specificity and sensitivity of the "tests" for terrorism, I mentioned this problem oh, 10 years or so ago. I guess it's about time people start catching on.
"In order to make an apple pie from scratch, you must first create the universe." -- Carl Sagan, Cosmos