Every day millions of industrial, commercial and military secrets travel around the world by cable and satellite... a spy's dream. How secure are modern computer systems? Is computer-bugging a hacker's prank or professional international espionage?
Fred Harris joins the army on manoeuvres and discovers whether data is secure on the battlefield.
Ian McNaught-Davis explains how data encryption works, and there's news of The Listener Crack the Code competition and its prizes.
Lesley Judd casts an eye over the winners of the Computer Animation Film Festival with John Vince, one of the judges.

Programme notes, updated monthly, are available on Ceefax page 700: on the Micro Live Bulletin Board - [number removed]: on Telecom Gold - type Info BBC: or, if you don't have the technology, send sae and a cheque or postal order for 50p to [address removed]