The five operational stages of a computer system which may be attacked by a criminal are input device, programming, the central processing unit (computer brain), output, and data communications. The complexity of a computer system operation, while allowing discovery of criminal manipulation, seldom enables prosecution of specific offenses. This is also due to the lack of Federal statutes proscribing the use of computers for criminal purposes. Recourse is possible to other provisions of the U.S. criminal code, including the theft and related offenses section of the code. Such judicial decisions as United States v DiGilio (1976) and United States v Hubbard (1979) are cited in support of Section 641's effectiveness, with the caution that some questions raised by Section 641 have not yet been settled by the courts. Section 2314, which makes it a felony to transport stolen goods, has also been applied to electronic data and signals, although this extension of the term 'stolen goods' to computer data has been challenged. Because of its versatility, the mail fraud statute, Section 1341, has been successfully used as a weapon to prosecute computer crime. However, new developments in computer technology, such as electronic funds transfer systems, have produced corresponding computer abuses. A further problem for the prosecution is the admissibility of evidence provided by computer printouts instead of by eyewitnesses, forcing reliance on hearsay and best evidence rules and their respective exceptions. Footnotes are included.