Security agencies around the world are faced with difficult times with the number of terrorist threats there are today. Identifying and monitoring suspected terrorists is a challenge that is testing all of the agencies as they try to protect people.

Who really is a threat and which individuals are not is a difficult assignment. It is almost impossible to predict when an extremist’s emotions will explode into violence. Take the killing of a British soldier in daylight on a London street last week. The authorities have two suspects who had been on Britain’s spy agency radar, but there were no indications of when they might explode and cause deadly harm. The butchering of the soldier was one of the most brutal killings in the country’s history.

Authorities believe it was a random killing. One of the suspects had been seen at extremist demonstrations. The attack on the soldier was captured on video. One of the suspects was angrily complaining about the British government and troops in foreign lands. It isn’t clear whether the soldier was known by his attackers, who were both shot by police. They are recovering.

At the Boston Marathon bombing, one of the suspects had been known by authorities as a possible religious extremist, but that is about all they knew. The suspects were investigated, but the FBI found nothing to link them to terrorists.

It is impossible to watch them constantly. It is impossible to know when they will act. That is what is so difficult in protecting people from the attackers.

There are more religious extremists today than ever. There are more violent extremists around the world. We are going to need more undercover officers and there will be more surveillance cameras installed. However, there is no way to obtain 100 percent security.

Security measures, both in more personnel and equipment, are growth industries.