The absence of, or inadequate provision for, documentation and access controls for computer installations, facilitates computer crime. Unauthorized access to software and hardware is almost exclusively the means of crime perpetration. With authorized access, but with criminal collusion, two or more persons may commit crimes unnoticed, until financial audits, inventories, and computer operation system checks uncover the fraud or misuse. In the case of theft of intangible properties such as computer-stored patents of engineering, chemical or other designs, processes, or marketing and strategic data, the crime is exposed, if at all, by inferences drawn from the activities, products or knowledge shown by competitors.
Few computer crimes are actually reported. In the US is required by law to report computer crimes; many commentators agree that only about 15% of computer-related crimes are actually reported. The Australian Computer Abuse Research Bureau argues that only one in 20 cases of the $2 million or so worth of computer-related offences in Australia during 1980 was in fact reported. The reasons given are that there is not much faith in the legal system and its ability to prosecute a case of computer crime successfully; that companies fear that to declare publicly that their system has been breached and that their assets are not as secure as once thought will cause a flight of capital in shareholder's funds and deposits; and that there is a reluctance to expose the company's records and systems to public scrutiny and competitors.
In the UK in 1989, it was estimated that the cost to industry of computer-based crime was over £400 million per year. The average annual incidence was9 incidents per 100 companies (rising in some cases to 1 in 2), costing on average £46,000 per incident. Other estimates put the cost of computer crime as high as £2 billion per year. The most vulnerable sector is the communications industry in which there were 192 incidents per 100 companies. Fraudulent input of information, notably on payroll systems, accounted for 4.1 million pounds of losses.