a computer program that automatically copies itself, thereby "infecting" other disks or programs without the user knowing it, and then plays some kind of trick or disrupts the operation of the computer.

Viruses have existed as academic pranks since the 1960s, but 1987 saw the first malicious viruses, apparently the work of disgruntled programmers trying to sabotage their competition.

Nowadays, most virus infections result when the user of a computer is tricked into running a malicious program by opening it as a file. To avoid viruses, never open a file that arrives unexpectedly in e-mail, even if it's from someone you know and trust (see worm virus). Always run antivirus software; keep your antivirus software up to date; and always install software from the manufacturer's original disks rather than from copies made on a potentially infected machine.

Knowingly spreading a computer virus is a crime under common law and under specific laws in various states.

a law passed by the U.S. Congress in 1996 making it illegal to transmit indecent material to children through the Internet. In 1997, the Supreme Court declared this law to be unconstitutional on the ground that the Internet is inherently entitled to the same freedom of speech as printed media, and that there is no practical way to block material from reaching children while transmitting it freely to adults.Seeindecency and cross-references there.

Note that the Communications Decency Act is separate from laws against pornography, including child pornography, and such laws were not affected when it was overturned.

protection given by law to authors of literary, musical, artistic, and similar works. The copyright holder enjoys the following exclusive rights: (1) to print, reprint, and copy the work; (2) to sell, assign, or distribute copies; and (3) to perform the work. A copyright is recorded at its acquisition price. The legal life of a copyright is the life of the author plus 70 years. Rarely will the economic life of a copyright exceed its legal life. For example, some textbooks become obsolete in five years. As other limited life intangible assets, copyrights are amortized over the period benefited.

laws that are designed to keep markets competitive, rather than allowing them to be dominated by monopolists. The main U.S. antitrust law is the Sherman Antitrust Act. Section 1 of this law makes it illegal for sellers of a product to join together to raise the price of the product. Section 2 makes monopolizing acts illegal. However, it does not automatically make having a monopoly illegal, since an inventor with a patent has a legal monopoly on that invention. It is illegal to acquire a monopoly through anticompetitive means, but the exact meaning of the law depends on how the courts interpret it. An antitrust case was filed against IBM in 1969 because of its dominance of the mainframe computer market in the 1960s. The case dragged on until 1982 when it was finally dropped because the technology had changed so much that it was no longer relevant.

a piece of information (usually about the design or manufacturing of a product) that is kept secret because it gives the maker an advantage over competitors. A famous trade secret is the formula for Coca-Cola.

The security of a trade secret depends on successfully keeping outsiders from knowing it. Patents, by contrast, are openly disclosed to the public, with a prohibition against unauthorized use.

The internal workings of most software packages are trade secrets, but it is somewhat unclear whether software licenses can actually prevent people from analyzing the working of machines that they own.

a controversial law passed by the U.S. Congress in 1998 designed to secure copyright protection of digital works.

Unlike earlier copyright laws, the DMCA prohibits not only copying, but also the use of technology to get around technical measures designed to prevent copying, even when the copying itself is legal. "No person shall circumvent a technological measure that effectively controls access to a work protected under this title" (17 USC 1201). The law also makes it illegal to distribute circumvention technology.

Critics argue that the DMCA is badly flawed. It prohibits people from experimenting to learn exactly how certain software works even when that software is running on their own computers, and unlike all earlier copyright laws, the DMCA enables copyright owners to block people from reading and viewing material that they possess, not just copying from and redistributing it.

the main U.S. law against wiretapping and other interception of private electronic communications, whether they are transmitted by wire, radio (including wireless network), or other means. It was passed in 1986 and superseded a number of earlier laws.

Critics point out that the ECPA does not require the sender of a message to encrypt (scramble) it to make it private. Thus, private messages can still be intercepted deliberately or even by accident. For example, first-generation analog cellular telephones were assigned to frequencies formerly occupied by UHFTV channels, and they used the same kind of modulation as TV sound. Thus, telephone calls could be picked up on old television sets. Similarly, radio technicians tracking down sources of interference could find themselves hearing things that are illegal to listen to.

On the whole, however, the ECPA is an essential part of the laws protecting computer networks and communication systems from tampering and eavesdropping. It is one of the laws most commonly violated by crackers.

exclusive right given by the government to the company to use, manufacture, and sell a product or process for a nonrenewable 20-year period without interference or infringement by other parties. Patent is classified as an intangible asset. Costs such as registration fees and attorney costs incurred in obtaining the patent are capitalized. Research and development costs applicable to developing the product, process, or idea are immediately expensed. Legal costs of a successful defense of a patent are capitalized and amortized over the remaining life. If the patent right is lost in court it should be written off and shown as an extraordinary charge. The cost of a patent purchased from an outsider is deferred and amortized. If the sole purpose of buying the outsider patent is to eliminate the competition, the amortization period is the remaining life of the company's patent that is being protected. The patent is amortized on a straight-line basis over its 20-year life, or its economic life, if less. As a practical matter, often the useful life is less than 20 years due to changes in the marketplace and new technology. If a patent is assigned to others, royalties obtained are accrued as revenue is earned.

publications or images whose primary purpose is to stimulate sexual appetite.See also indecency; obscenity.

Even the most innocent Internet user occasionally stumbles upon pornography. Some pornographers send advertisements to all the email addresses they can obtain or make up (seespam). (Such e-mail does not indicate that the recipient has been viewing pornographic web pages, even if it says that it does.) Others rig their web pages so that search engine will lead users to them who are looking for something else.

Many individuals find pornography strongly addictive. The purpose of pornography is to make money, and the only reason it is given away free is to get people "hooked" so that they will pay for more.

In the United States, most of the pornography on the Internet is legal, but sexually explicit images of children are not, and images of sexual behavior may not be legal, depending on local laws. (See obscenity; computer law.) Law enforcement is hampered by the difficulty of determining the physical locations of web sites. Note however that because the laws prohibit distribution of obscene material, a link to an obscene site can itself be illegal.

There have been various efforts to keep pornography from reaching children and unwilling audiences. The Communications Decency Act of 1996 was struck down because it assumed, incorrectly, that Internet service providers can control the information sent through their computers; replacement legislation has been proposed. Schools and libraries sometimes use "filtering" software to block access to known pornographic web sites, but the filtering process is imperfect. See ICRA.

Pornography is associated with credit card fraud and other crimes. Several Internet pornography vendors have been caught making unauthorized charges to credit card numbers, presumably expecting the victims to be too embarrassed to complain. In some cases the numbers were stolen or made up and belonged to people who had never had any contact with the vendors.

It is naive to describe pornography as "victimless." The most obvious victims are the individuals who become addicted, and whose relationships and even marriages are damaged. The young people hired to pose for pornographic pictures are also victims of exploitation.

legal document issued by a regulatory agency permitting an individual to conduct a certain activity, usually because the person has passed a training course qualifying him. For example, a securities license is required for a broker to sell stocks, bonds, and mutual funds. An insurance license is required before someone can sell insurance products. Before a driver's license is granted, a driver must pass an examination proving that he knows how to drive safely. If the licensed individual violates the regulations, the license can be revoked.

a get-rich-quick scheme in which you receive a message containing a list of names. You're expected to send money to the first person on the list, cross the first name off, add your name at the bottom, and distribute copies of the message.

Pyramid schemes are presently common on the Internet, but they are illegal in all 50 states and in most other parts of the world. They can't work because there is no way for everyone to receive more money than they send out; money doesn't come out of thin air. Pyramid schemers often claim the scheme is legal, but that doesn't make it so.

a policy established by the owner of a computer system, or by an Internet service provider, concerning acceptable use of the computer and network facilities. Acceptable-use policies should generally include the following points:

1. Users are accountable for what they do. Deliberate snooping, harassment, or interference with other users will not be tolerated, nor will any deliberate unauthorized activity.
2. The computer shall be used only for its intended purposes. For example, you generally can't use your employer's computer to run another business on the side; nor can you run private moneymaking schemes on a computer owned by a state university.Employees are accountable for how they use their time at work.
3. Passwords must be kept secret. Seepassword.
4. The service provider has the right to suspend accounts that are being misused. People accused of misconduct have the right to a fair hearing.
5. Users must abide by the acceptable-use policies of newsgroups and other electronic discussion forums, which are mostly paid for by other people. On the Internet you are always someone's guest.
6. Chain letters and mass e-mailing are expensive, unwelcome, and generally not permitted. The correct way to reach a wide audience is to use an appropriate newsgroup.
7. Cyberspace is not above the law. Practices that are illegal in the real world, such as forgery, gambling, obscenity, and threatening or inciting violence, are still illegal when you do them on the computer.
8. Losing an account is not necessarily the only penalty for misconduct. The service provider cannot shield users from criminal or civil liability when they break laws or deliberately harm others. Really destructive computer abusers generally have several accounts and must be stopped by other means.

a popular, but often illegal, online form of recreation. Internet casinos are World Wide Web sites that offer games of chance, with the ability to place bets and receive money. Users are often under the impression that this activity is beyond the reach of local laws, but actually, gambling laws do not make any exemption for computers. U.S. federal law specifically prohibits placing bets "by wire" unless the gambling is legal at the locations of both parties.

A further difficulty is that there is no way for the casino operator to tell whether the players are human beings. Some of them could be computer programs, simulating the behavior of a human being at a web browser, and meanwhile collecting detailed information about the workings of the casino - the ultimate card sharp, so to speak. The feasibility of doing this has been demonstrated by Paul Apostolik at The University of Georgia, although, for legal reasons, no actual money was wagered. See computer law.

Usage note: In the computer world, gaming does not mean gambling. It means playing computer games for recreation.

the status of literature, art, music, or software that was not copyrighted, or whose copyright has expired and not been renewed.

A computer program is in the public domain if it is not covered by any kind of copyright. Few substantial public-domain programs exist, but the term "public domain" is often used incorrectly to describe other kinds of freely copyable software (see free software).