Passage Four
Every country has secret services to help protect it against serious threats from terrorists, major criminals or even from other countries. People who threaten to harm a country always plot in secret, so the intelligence agencies have to work in secret to find out what is being planned before it happens, so that it can be prevented. They do that in many different ways – by secretly listening to their targets talking on the phone, by planting microphongs to overhear meetings, by watching the targets as they move from place to place and by recruiting some of the targets to act as double agents to report on what is going on.
For most of my career I worked in one of the UK’s three intelligence services, MIS, the domestic security service. I first joined in the 1970s, in the middle of the Gold War, when the war was divided into two armed camps, the Soviet Union(苏联) and its allies on the one side and Western Europe, America and their allies on the other. The Gold War never became a fighting war. It was an intelligence war, with intelligence officers from both sides trying to find out what the other side was doing, what kind of weapons they had, when and if they might start a war and what their plans were. Both sides were secretly working in each other’s countries.
Nowadays one of the biggest threats to the world, comes from terrorists. Intelligence officers from many differenct countries are working together to find out who they are., where they are and what they are planning. Today’s MIS officers get their intelligence in much the same way as we did during the Gold War, but their task is even more difficult and urgent because most terrorists want to kill people. Many terrorist attacks that are planned and prepared never happen, and we never know anything about them because the intelligence services find them out and prevent them.

What is the first paragraph mainly about?