Anti-terrorism intelligence monitors "electronic chatter" to see when attacks are imminent - but what exactly is it? Where does it come from and how is it monitored?
It happened in the weeks before 11 September, 2001, in the run-up to the Bali bombing last October, and ahead of the suicide blasts in Riyadh - a surge in "electronic chatter", then sudden silence shortly before each attack.
Now the United States is on heightened alert at home and in Saudi Arabia after intelligence agencies picked up "chatter" about new attacks against western targets. Both the US and UK have temporarily closed their embassies in the kingdom.
Similarly, British Airways has cancelled flights to and from Kenya amid fears of an attack on a UK plane, an alert said to have come from electronic eavesdropping on al-Qaeda suspects.
"Chatter" is the innocuous-sounding term for intercepted phone calls, e-mails and faxes between those suspected of plotting terror attacks.
Not that the agencies involved - among them MI5, the Government Communications Headquarters (GCHQ) at Cheltenham, and the US's National Security Agency (NSA) - will discuss chatter and how it is monitored.
Mobile phones are among the easiest communications devices to scrutinize. When Army tanks rolled in to protect Heathrow against a possible missile attack last February, the GCHQ - which usually listens in on communications abroad - tuned into domestic airwaves to try to pick up any conversations of a hidden terror cell.
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"They may track how long a call is made for; where a call is made from and to; the number of calls made or e-mails sent."
Others may track postings on newsgroups known to be used by those of interest to the authorities, be they May Day protesters or a group altogether more sinister.
"Terrorists the likes of al-Qaeda know they have to be very careful about how they communicate, and some - like Osama bin Laden himself - prefer to use non-electronic means. There were reports of communicating by horse-back in Afghanistan, sending messengers to deliver face- to-face communications."
For a phone call gave away the Karachi hide-out of Ramzi Binalshibh, the senior al-Qaeda suspect caught last September. It is thought a sample of his voice - recorded from an al-Jazeera interview - was fed into the NSA's computers; within days he made a satellite phone call, and the US had a location.
And an intercepted e-mail led to the arrest last March of another suspected bin Laden aide, Khalid Sheikh Mohammed. As "chatter" indicated he was planning further attacks, satellite tracking of his associates' communications threw up an e-mail with his address.
When Dixie Chick Natalie Maines took the stage in London and told fans that she and her fellow Texas-born chicks were ashamed that George W. Bush was a Texan, it started a nationwide backlash against the group. Listeners flooded country music stations with demands they stop playing Chicks songs, fans sent their CDs in to be burned and conservative talk show host Mike Gallagher announced an alternative concert when the Chicks kick off their national tour in Greenville, S.C. on May 1.
Good old American pride? Not entirely. Turns out the boycott was orchestrated by political operatives of the National Republican Party.
Working out of the national headquarters, these operatives spammed GOP email lists the day after Maines made her statement, urging them to contact radio stations and demand they stop playing songs by the Chicks. Phone calls went out to country stations, urging them to remove the Chicks from their playlists. The "alternative" concert, supposedly promoted by Gallagher, is actually the work of the South Carolina Republican Party, who rode herd on a resolution through the state assembly condemning the chicks and party officials are helping promote the concert.
Earlier this week, we received a call from "Gallagher's Army," urging us to support the alternative comment. Caller ID backtraced the call to the South Carolina GOP Republican headquarters.
"We needed something to galvanize support for the war," brags one GOP operative. "Natalie Maines gave it to us on a platter."
