Tuesday, March 2, 1999 Published at 13:53 GMT
Satellite hijack 'impossible'
The latest Skynet satellite blasted off on Saturday
A senior defence industry analyst is contesting computer hackers' claims to have altered the course of one of the UK's military communications satellites.
Scotland Yard's Fraud Squad is investigating allegations of blackmail at several international locations after the hackers reportedly demanded a ransom payment to stop interfering with a Skynet satellite.
However, Paul Beaver, group spokesman for the Jane's Information Group, told BBC News Online: "I cannot see how it is possible for someone to hack in - it is a closed loop system, not connected to the Internet.
"You cannot get in unless you get in the way of a microwave signal or are at one of the Ministry of Defence's (MOD) sending locations. The only way in would be through the American system during a time of war, but this is not a time of war.
The MOD told BBC News Online: "The story is complete nonsense. All our satellites are where they should be and doing what they should be doing. It's all systems go."
But a hacking expert, David Levy, says: "They would say that, wouldn't they? To say you can't do something is ridiculous.
"When people say something in software or hardware can't be done, they are being unrealistic. What they mean is they can see no way it can be done.
"The RSA encryption algorithm was supposed to be uncrackable until two guys in Cambridge University did it. Nothing is impossible."
Mr Levy runs Tiger Computer Security. The firm advises companies on security by hacking into their systems and then explaining how to close the loopholes they find.
Skynet is essential
The fifth Skynet satellite was launched on Saturday from French Guyana. The network provides support for strategic and tactical nuclear forces and maritime, air and land forces. The MOD describe Skynet as "essential to support all aspects of modern military operations".
They are controlled by microwave signal. Unlike radio waves, which spread out in all directions, the microwaves used have a "pencil" beam. This spreads by only three centimetres for every 10,000km travelled.
The location of the sending stations means that anyone wishing to intercept and change the signals would have to build a tower in south-west London.
An alternative might be to send signals directly but Mr Beaver says: "This would require a "very, very high-powered transmitter and someone would have detected that. You can't just move your satellite TV dish around."