http://www.fas.org/irp/program/process/echelon.htm


ECHELON

ECHELON is a term associated with a global network of computers that
automatically search through millions of intercepted
messages for pre-programmed keywords or fax, telex and e-mail addresses.
Every word of every message in the frequencies
and channels selected at a station is automatically searched. The processors
in the network are known as the ECHELON
Dictionaries. ECHELON connects all these computers and allows the individual
stations to function as distributed elements an
integrated system. An ECHELON station's Dictionary contains not only its
parent agency's chosen keywords, but also lists
for each of the other four agencies in the UKUSA system [NSA, GCHQ, DSD,
GCSB and CSE]