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mutually faithful to the relationship.’ ‘Casual kissing appears to be safe. Open mouth kissing appears to be more dangerous. It is that which follows open mouth kissing that is most risky.’ ‘AIDS virus may appear in small quantities in the tears of an infected person. However exposure to tears is not likely to be a major mode of transmission of the disease.’

The AIDS trojan, as it had quickly become named, also produced a variety of messages demanding payment for the licence. In certain cases, if the computer was linked to a printer, it could cause an invoice to be printed out. The money for the licence was to be sent to PC Cyborg Corporation at a post office box in Panama City, in Panama. It was not specified what users would receive for the fee, apart from a licence. It was assumed, however, that an antidote for the trojan would be included in the deal.

The AIDS Information diskette was the largest and most complex trojan Jim had ever seen. He worked on it eighteen hours a day for seventeen days; he later said that taking apart the program was ‘like peeling an onion with a paper clip’. His final disassembly ran to 383 pages, each containing 120 lines of code. He had managed to produce a quick antidote to the AIDS trojan on the day he received it: after he had disassembled the bug, he put together a program called ‘ClearAid’ which would restore files and cleanse infected systems. The antidote and ClearAid were offered free to infected computer users by Jim and PC Business World.

Later, when the furore died down, Jim decided the trojan had been written ‘by a young inexperienced programmer with only scant knowledge of both the language and the machine capabilities at his disposal.’ Its tortuous complexity had been caused by incompetence rather than design.

This was little comfort for those institutions that had suffered damage from the bug. It had been discovered that over 20,000 of the AIDS diskettes had been sent out, using the mailing list provided by PC Business World, the delegate register to a World Health Organization (WHO) conference on AIDS in Stockholm and other address sources in Italy and Holland. In the first few days, a number of recipients had panicked when they realized they had just loaded a potentially destructive trojan on to their systems. At the UN Develop-

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