''Legally we can be in trouble if we inadvertently transmit a virus,' explained Mr Campbell, sales director of Reflex Magnetics, which duplicates computer disks for software houses, publishers and other organisations. Software houses need duplicated diskettes containing their product in order to sell them; organisations such as insurance companies regularly need to send out quotations and other material to their representatives; and computer magazines increasingly attach diskettes of free software to their covers.
Reflex Magnetics had always virus-scanned the material that was sent to it for duplication, because were a virus to become lodged in its computer system, it could be transmitted many times over - perhaps infecting a magazine disk one week, an insurance companies' quotations the next. In the first five years since its formation in 1985, the company had never actually detected a virus. 'Then suddenly we were seeing a great incidence - three separate attacks over a few months,' Mr Campbell related.
Reflex began considering what it could do to address the problem. There were a number of anti-virus products on the market, but they were dismissed as inappropriate for Reflex's needs. 'Existing virus- scanning products just picked up a virus after the disk or PC had already been infected,' Mr Campbell said. 'They did not adequately control the use of disks within an organisation.'
Although many organisations do have internal rules prohibiting the use of people's own computer disks, or game software, on office computers - at least until they have been scanned for viruses - such procedures are extremely difficult to enforce. They also prevent users bringing disks to the office containing material that they have been working on at home.
Consequently, the rules are often ignored. And the greater the number of computers in a network, the higher the probability of a virus from a rogue disk fed into a single computer.
What was required was a way to identify individual disks as free of viruses and thus acceptable to be fed into computers all around an organisation or over a network - and to recognise when the material on the disk had been changed by computers not belonging to the organisation.
Mr Campbell, who is not a programmer himself, produced a specification for some software to do just that. The company then had the software specification turned into a program by Dr David Aubrey- Jones, at the time a consultant to the company, now its technical director.
'The software examines the contents of each disk fed into the computers on an organisation's network and writes a 'check sum' on it,' Dr Aubrey- Jones explained. 'The disk can be read from, and written to, quite readily by computers on the network, with the check sum being changed each time. But when the disk's contents are changed by a computer not running the software, the check sum cannot be changed - indicating the possibility of a virus when the disk is fed back in.'
Although the software was originally developed to safeguard Reflex's own operations, Mr Campbell confesses that the commercial possibilities occurred to him 'about five minutes after first thinking of the idea'.
Formally marketed as Disknet since 1992, the software is used by more than 70 blue-chip organisations in the UK and the US - including the armed services, the Department of Trade and Industry and parts of Midland Bank. Sales are expected to top pounds 1m this year, which is already a fifth of the size of Reflex's original disk duplicating business - and growing much faster.
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