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514 GCHQ GOES GLOBAL
kidnappers of the American journalist Daniel Pearl, who was
murdered by his captors in early 2002, contained deliberately
misspelled words, such as 'Amreeka', 'Terrarism' and 'Pakstan',
designed to avoid alerting the authorities. 16 Nevertheless, good
communications security discipline is difficult, and one slip by
the terrorists could give away a key player.17
Terrorists and drug dealers alike had also learned to change
their mobile phones and sim cards frequently, as often as once
every three days. The sigint agencies responded by using
recorded 'voice prints', which allowed them to search volumes
of traffic for people who 'sounded like' the suspects. The British
were apparently the first to provide an authentic recording of
bin Laden's voice, which was then used in this way. IS The technique
also revealed the location of Ramzi Binalshibh, a senior
al Qaeda operative who was caught in Pakistan in September
2002. It appears that a sample of his voice, taken from an al­
Jazeera television interview, was used to conduct a computer
search against vast volumes of telephone traffic collected by
satellite. Exactly a year after the 9/11 attacks, on the morning
of Wednesday, 11 September 2002, the Pakistani intelligence
service, lSI, surrounded a four-storey block of flats in Karachi.
Their initial assault surprised five men who had returned to
bed in one of the apartments after early-morning prayers. While
they were being taken out at gunpoint, sympathisers in the
adjacent apartment threw a grenade at the intelligence officers.
A gun battle developed, and those inside hurled more
grenades at the authorities. 19 Terrified neighbours called the
local police, who were unaware of the super-secret activities
of the lSI. In the ensuing confusion twenty policemen were
injured, many by friendly fire. 20 Ramzi Binalshibh was among
those captured.
In the spring of 2003 an intercepted email led to the arrest
of Khalid Sheikh Mohammed, who was very close to bin Laden,
and had been a key figure in the planning of the 9/11 attacks. 21
He was arrested at a house in Rawalpindi in a joint operation
by lSI and the CIA's paramilitary force, the Special Activities