Is terrorism a traditional or non-traditional threat to security?

Terrorism is non traditional concept. As Non-traditional threats are generally seen as those threats which are emanated by the non-state actors
Terrorism is, in the broadest sense, the use of intentionally indiscriminate violence as a mean to create terror, or fear, to achieve a political, religious or ideological aim.

It is due to political violence that targets civilians deliberately and indiscriminately. Terrorist group seeks to change a political context or condition that they do not like by force.

The classical examples of terrorism involve hijacking planes or planting bombs in trains, cafes, markets.