On September 11, 2001, the world changed with the devastating attacks on the World Trade Center in the United States. In the years after, the threat from terrorism has also morphed. As more resources have been poured into fighting terror, so have the tactics of terrorists changed.
While the 9/11 attacks were planned meticulously and executed by men trained for the deadly task, many of the attacks in recent years have been carried out by so-called lone wolves. They may be smaller in scale but harder to detect and prevent.