The Cold War might be over and Communism, arch-enemy of the USA, might have been consigned to history but that does not mean that Washington's intelligence gathering agencies have become extinct.

In fact, in today's dangerous and uncertain world they are very much still in business. The Central Intelligence Agency (CIA) remains a major player in influencing government policy and its director is very much at home in Washington's corridors of power.

Some things, of course, are different but the importance placed on the gathering of accurate intelligence and countering threats is as crucial today as it was in the days of the Iron Curtain and the Berlin Wall. Today's spooks are equipped with a dazzling array of modern gizmos, everywhere the computer is the queen of the intelligence battlefield, pilotless drones can gather real-time intelligence and no conversation can remain secret for long.

The global war on terror has changed everything too. Much more is known about the dynamics of Islamic fundamentalism and while enemy cells are difficult to infiltrate it can be done even though it is expensive and time-consuming. Above all, in the most difficult and dangerous arenas, cyber warfare is an important key to breaching the opposition's defences. For example, in the Middle East today, for every jihadist gunman ready to embrace eternity there is an army of computer geeks whose expertise can be equally deadly.

Control the internet and you have access to a global communications system which can influence minds and change them. The same environment provides secure communications, anonymity and the capacity to instil fear in others - all vital ingredients in the world of espionage. And yet in the midst of this hall of mirrors which passes for a battlefield some things never change. The chief one is known by the spooks as "humint" - human intelligence. That is why the US National Intelligence Agency (NSA) places so much importance on maintaining its army of intelligence gathering operatives and that helps to explain the angst felt when that security is breached or when an agent goes rogue.

That happened last year when one of its agents, Edward Snowden, had a brainstorm or an attack of conscience and decided to reveal the extent of NSA's activities to the world. Some of the information was deeply disturbing as no one knew what this secretive organisation got up to inside its headquarters in Maryland. According to Snowden's leaked documents, the NSA intercepts the communications of more than a billion people and tracks the movement of hundreds of millions of people using their mobile phones and listening in to their conversations. Many of these individuals turned out to be world leaders of countries which are US allies.

Snowden's revelations showed that the NSA created or maintained security vulnerabilities in most software which meant that users of the internet were vulnerable to cyber attacks. Within the USA the agency carried out large-scale surveillance of US citizens.

Snowden's evidence was deeply concerting and caused outrage across the world. By way of response senior figures in the agency pointed out that the NSA's phone and internet intercepts had been instrumental in preventing 54 terrorist "events", including 13 in the US, and in all but one of these cases had provided the initial tip to allow arrests to be carried out.