In order for terrorist organizations to be identified, some specific characteristics have to be determined according to section 219 of the INA (Immigration and Nationality Act)
These organizations have to endanger national security, be active and be responsible for planning and carrying out previous attacks.
An FTO is considered such if it fulfils the following criteria:
- The organization has to be foreign.
- The activities carried out by this organization have to endanger or threaten national security.
- The organization has to take part in, or have the ability or intention to take part in a terrorist attack.
For these types of organizations to be put in the State Department's list, the Bureau of Counterterrorism in the State Department (also known as CT) investigates and monitors the activities carried out by groups that could possibly be considered FTOs.
I personally think this method is very useful and helps prevent future attacks. Also, this classifying methods help distinguish organization that could potentially create massive chaos and possibly the death of innocent people.