Although this is a futuristic example of the potential use of computers in the sex industry, there is growing concern about a much less esoteric phenomenon - the dissemination of pornographic material either as computer diskettes or over computer networks.

Computer pornography is not a new issue: in the early days of personal computing there was justifiable outrage over the dissemination of crudely-drawn computer games with sexist and racist themes.

What is new, however, is the quality of the images that modern technology makes possible and the ease with which they can be disseminated, especially where young people are involved.

Diskettes can be swapped in the playground; computer bulletin boards can be accessed by home computers. Regulation is difficult, if not impossible.

Mr John Ashley of Greater Manchester Police, a specialist in obscene publications, said there was no pornographic image, still or moving, which could not be captured on floppy disk or disseminated over a network.

The computer pornography now being distributed in Britain seems to be coming from the traditional sources - the United States and The Netherlands.

There is a real and serious problem, according to Ms Catherine Itzin of Bradford University, whose book Pornography has just been published by Oxford University Press.

Mr Ashley and Ms Itzin believed it was impossible at present to regulate computer pornography.

Mr Ashley, indeed, did not foresee any technical developments which would improve matters.

His approach was to prosecute when possible, and he believed it had a salutary effect.

The Law Specialist group of the British Computer Society (BCS), the chartered institution for information technology specialists, has set up a consultative group to examine two questions.

First, are there technical answers to the problem of regulation? Second, what are the legal implications of pornography in this form and are changes in the law required? The BCS, aware that what is pornographic can often be a matter of opinion rather than fact, is directing its campaign towards the protection of young people.

That computers have become a medium for pornography is not in itself of any more significance than the more traditional use of books or films. But computing has special characteristics.

Mr Ron McQuaker, BCS vice-president responsible for professional affairs, argued that a diskette was unlike a magazine or a videotape.

Its contents were not obvious and it could be protected by passwords; it could be programmed to self-destruct if the wrong key was used.

There is no real answer, technical or otherwise, to the issue of pornography, apart from changes in social attitudes.

But a technical trap for pornographers might open the possibility of catching virus writers and others who misuse computer systems.