These errors are known as 'logic bombs' - small sections of code hidden in the body of a legitimate program and activated by a pre-programmed trigger. Logic bombs can simply leave the software 'hanging' or can create expensive problems, such as destroying data if the software writer's demands are not met.
The legal position is not yet clear. If software writers warn clients - even if only in the small print of a contract - that a bomb is in place, they may still be within the law. If they fail to give prior warning, they might be at risk of prosecution under the Computer Misuse Act of 1990.
There have been only a handful of court cases in this field, although legal action expected in the north of England in the next few weeks may help to clarify some grey areas. A man from the Cheshire area has been interviewed in connection with an alleged offence under the Act committed in Goole, Humberside. Police expect to submit a file on the case to the Crown Prosecution Service in the next few weeks.
But some people in the programming world openly acknowledge the use of logic bombs as an acceptable way to collect money from clients who default on fees. Edward Wilding, editor of the Virus Bulletin, said that he had come across several cases.
Mr Wilding said companies could expect the problem to escalate as redundancy and lack of contract work threaten programmers' livelihoods. 'Employers should be aware of the potential of the enemy within - the disgruntled employee. It is becoming accepted practice for these people to be marched off the premises within minutes but by then it may be too late.'
One logic bomb, planted in the US, backfired on its creator to the tune of dollars 25,000. Earlier this month Donald R Lewis was ordered to compensate a Manhattan law firm whose computer system crashed because of a glitch he had added.
He had hoped to force the company to call him in for repair work but the firm paid a different consultant dollars 7,000 to repair it.Reuse content