DRIVING ALONG the highway between Washington DC and Baltimore you come across a relatively innocuous sign marking the turn-off to Fort Meade.
If you follow it over a rise and behind some woods, you will not get much further. A vast network of fences looms ahead. Fort Meade is the ultra-secret heart of the United States' intelligence community - home of the National Security Agency (NSA).
Most people have heard of the more famous parts of the US spy troika - the domestic Federal Bureau of Investigation and the external Criminal Intelligence Agency. But the NSA has long lurked in even darker shadows as it monitors electronic communications across the globe.
When then-president Harry Truman issued an executive order for its creation in 1952, even the founding document remained a state secret for years - leading to its own staffers creating their own acronym 'No Such Agency'.
But various espionage scandals threw the spotlight upon the Cold War excesses of the intelligence community back in the 1970s, from coup plotting to surveillance of American civil-rights workers and rock stars.
And now, the NSA is back in the news again. The 24 crew members of the US Navy EP-3E spy plane recently detained on Hainan Island were running an NSA electronic eavesdropping operation. The European Parliament is currently investigating claims that the US is misusing its international NSA network to listen to ordinary Europeans' phone calls to supply commercial intelligence to American firms.