International review of criminal policy - Nos. 43 and 44/Common types of computer crime

E. Common types of computer crime

61. All stages of computer operations are susceptible to criminal activity, either as the target of the crime or the instrument of the crime or both. Input operations, data processing, output operations and communications have all been utilized for illicit purposes. The more common types of computer-related crime are categorized next.


 * 1. Fraud by computer manipulation

62. Intangible assets represented in data format, such as money on deposit or hours of work, are the most common targets of computer-related fraud. Modern business is quickly replacing cash with deposits transacted on computer systems, creating an enormous potential for computer abuse. Credit card information, as well as personal and financial information on credit-card clients, have been frequently targeted by the organized criminal community. The sale of this information to counterfeiters of credit cards and travel documents has proven to be extremely lucrative. Assets represented in data format often have a considerably higher value than traditionally targeted economic assets, resulting in potentially greater economic loss. In addition, improved remote access to databases allows the criminal the opportunity to commit various types of fraud without ever physically entering the premises of the victim.

63. Computer fraud by input manipulation is the most common computer crime, as it is easily perpetrated and difficult to detect. Often referred to as "data diddling", it does not require any sophisticated computer knowledge and can be committed by anyone having access to normal data-processing functions at the input stage.

64. Program manipulation, which is very difficult to discover and is frequently not recognized, requires the perpetrator to have computer-specific knowledge. It involves changing existing programs in the computer system or inserting new programs or routines. A common method used by persons with specialized knowledge of computer programming is the trojan horse, whereby computer instructions are covertly placed in a computer program so that it will perform an unauthorized function concurrent with its normal function. A trojan horse can be programmed to self-destruct, leaving no evidence of its existence except the damage that it caused. 13 Remote access capabilities today also allow the criminal to easily run modified routines concurrently with legitimate programs.

65. Output manipulation is effected by targeting the output of the computer system. The obvious example is cash dispenser fraud, achieved by falsifying instructions to the computer in the input stage. Traditionally, such fraud involved the use of stolen bank cards. However, specialized computer hardware and software is now being widely used to encode falsified electronic information on the magnetic strips of bank cards and credit cards.

66. There is a particular species of fraud conducted by computer manipulation that takes advantage of the automatic repetitions of computer processes. Such manipulation is characteristic of the specialized "salami technique", whereby nearly unnoticeable, "thin slices" of financial transactions are repeatedly removed and transferred to another account. 10


 * 2. Computer forgery

67. Where data are altered in respect of documents stored in computerized form, the crime is forgery. In this and the above examples, computer systems are the target of criminal activity. Computers, however, can also be used as instruments with which to commit forgery. The created a new library of tools with which to forge the documents used in commerce. A new generation of fraudulent alteration or counterfeiting emerged when computerized colour laser copiers became available. 14 These copiers are capable of high-resolution copying, the modification of documents and even the creation of false documents without benefit of an original, and they produce documents whose quality is indistinguishable from that of authentic documents except by an expert.


 * 3. Damage to or modifications of computer data or programs

68. This category of criminal activity involves either direct or covert unauthorized access to a computer system by the introduction of new programs known as viruses, "worms" or logic bombs. The unauthorized modification, suppression or erasure of computer data or functions with the internet to hinder normal functioning of the system is clearly criminal activity and is commonly referred to as computer sabotage. Computer sabotage can be the vehicle for gaining economic advantage over a competitor, for promoting the illegal activities of ideologically motivated terrorists or for stealing data or programs (also referred to as "bitnapping") for extortion purposes. In one reported incident at London, Ontario, in 1987, a former employee of a company sought unsuccessfully to sabotage the computer system of the company by inserting a program into the system that would have wiped it out completely.

69. A virus is a series of program codes that has the ability to attach itself to legitimate programs and propagate itself to other computer programs. A virus can be introduced to a system by a legitimate piece of software that has been infected, as well as by the trojan horse method discussed above.

70. The potential purposes of viruses are many, ranging from the display of harmless messages on several computer terminals to the irreversible destruction of all data on a computer system. In 1990, Europe first experienced a computer virus, used to commit extortion in the medical research community. The virus threatened to destroy increasing amounts of data if no ransom was paid for the "cure". A significant amount of valuable medical research data was lost as a result.

71. A worm is similarly constructed to infiltrate legitimate data-processing programs and to alter or destroy the data, but it differs from a virus in that it does not have the ability to replicate itself. In a medical analogy, the worm can be compared to a benign tumor, the virus to a malignant one. However, the consequences of a worm attack can be just as serious as those of a virus attack: for example, a bank computer can be instructed, by a worm program that subsequently destroys itself, to continually transfer money to an illicit account.

72. A logic bomb, also known as a "time bomb", is another technique by which computer sabotage can be perpetrated. The creation of logic bombs requires some specialized knowledge, as it involves programming the destruction or modification of data at a specific time in the future. Unlike viruses or worms, however, logic bombs are very difficult to detect before they blow up; thus, of all these computer crime schemes, they have the greatest potential for damage. Detonation can be timed to cause maximum damage and to take place long after the departure of the perpetrator. The logic bomb may also be used as a tool of extortion, with a ransom being demanded in exchange for disclosure of the location of the bomb.

73. Irrespective of motive, the fact remains that the use of viruses, worms and logic bombs constitutes unauthorized modification of legitimate computer data or programs and thus fall under the rubric computer sabotage, although the motive of the sabotage may be circumstantial to the alteration of the data.


 * 4. Unauthorized access to computer systems and service

74. The desire to gain unauthorized access to computer systems can be prompted by several motives, from simple curiosity, as exemplified by many hackers, to computer sabotage or espionage. Intentional and unjustified access by a person not authorized by the owners or operators of a system may often constitute criminal behavior. Unauthorized access creates the opportunity to cause additional unintended damage to data, system crashes or impediments to legitimate system users by negligence.

75. Access is often accomplished from a remote location along a telecommunication network, by one of several means. The perpetrator may be able to take advantage of lax security measures to gain access or may find loopholes in existing security measures or system procedures. Frequently, hackers impersonate legitimate system users; this is especially common in systems where users can employ common passwords or maintenance passwords found in the system itself.

76. Password protection is often mischaracterized as a protective device against unauthorized access. However, the modern hacker can easily circumvent this protection using one of three common methods. If a hacker is able to discover a password allowing access, then a trojan horse program can be placed to capture the other passwords of legitimate users. This type of program can operate concurrently with the normal security function and is difficult to detect. The hacker can later retrieve the program containing the stolen passwords by remote access.

77. Password protection can also be bypassed successfully by utilizing password cracking routines. Most modern software effects password security by a process that converts a user's selected password into a mathematical series, a process known as encryption. Encryption disguises the actual password, which is then almost impossible to decrypt. Furthermore, legitimate security software has been developed that allows access to data only after it checks encrypted passwords against a dictionary of common passwords so as to alert system administrators of potential weakness in security. However, this same security process can be imitated for illegitimate purposes. Known as a "cracker" program when used for illegitimate purposes, these tools encrypt some or all of the data of the system. This creates a dictionary of data to compare with cracker software, for the purpose of identifying common passwords and gaining access to the system. A variety of these system-specific encryption routines can be obtained from hacker bulletin boards around the world and are regularly updated by the criminal community as security technology develops.

78. The third method commonly used to access a system is the "trapdoor" method, whereby unauthorized access is achieved through access points, or trapdoors, created for legitimate purposes, such as maintenance of the system.

79. The international criminal hacker community uses electronic bulletin boards to communicate system infiltration incidents and methods. In one case, details of a Canadian attempt to access a system were found on suspects in an unrelated matter in England; they had removed the material from a bulletin board in Germany. Thissharing of information can facilitate multiple unauthorized infiltrations of a system from around the globe, resulting in staggeringtelecommunication charges to the victim.

80. With the development of modern telecommunications system, a new field for unauthorized infiltration was created. Personal telecommunications have been expanded with the advent of portable, cellular telecommunication devices. The criminal community has responded to these advances by duplicating the microchip technology.

81. Modern telecommunications systems are equally vulnerable to criminal activity. Office automation systems such as voice mail boxes and private business exchanges are, in effect, computer systems, designed for the convenience of users. However, convenience features such as remote access and maintenance capabilities, call-forwarding and voice-messaging are easily infiltrated by computer criminals.

82. Modern telecommunications systems, like other computer systems, are also susceptible to abuse by remote access. The integration of telecommunications systems means that once one system is accessed, a computer operator with sufficient skill could infiltrate the entire telecommunications network of a city. The usual motive for telecommunications crime is to obtain free telecommunications services. However, more innovative telecommunications fraud has also been uncovered, and telecommunications systems have been used to disguise other forms of criminal activity.


 * 5. Unauthorized reproduction of legally protected computer programs

83. The unauthorized reproduction of computer programs can mean a substantial economic loss to the legitimate owners. Several jurisdictions have dictated that this type of activity should be the subject of criminal sanction. The problem has reached transnational dimensions with the trafficking of these unauthorized reproductions over modern telecommunication networks.