FORTUNATELY for Michael Whelan, a book illustrator in Danbury, Conn., a friend of his was looking through a computer bulletin board and came upon a few of Mr. Whelan's images that were being offered for sale. Nowhere did it say that Whelan was the artist and, in fact, the copyright notice had been deleted. The images themselves had been somewhat altered: mountains were replaced by a sign that said "Welcome to the World of Macintosh."At least two copyright laws were violated by an unknown number of electronic services that had appropriated Whelan's work. His lawyer was able to track down two of those services, receiving a settlement. But the incidence of people stealing protected or copyrighted imagery for advertising designs or T-shirt decoration by "scanning" it into computers, is growing unchecked. Though Whelan's friend found his work on a computer bulletin board, New York City illustrator Bill Lombardo was a little less fortunate. His work was also discovered on a bulletin board, but "before I could bring a lawsuit, the company that had done this had gone out of business." It was slightly easier to steal Mr. Lombardo's work than Whelan's because Lombardo creates images directly on the computer - sending disks of his artwork to the companies that employ his services - whereas Whelan is a painter whose works were reproduced in books. Though companies may not allow material to be copied, the corporate culture can permit or discourage disregard for copyright concerns. To appropriate images, someone uses an electronic scanner to pick up the image from a book, print, or poster. The danger that scanners pose to an artist's copyright isn't a point of arcane concern for artists, as most major advertising agencies, design studios, and magazines have this equipment. Picture resolution is so good with computers that it is now far more difficult to determine which is the original and which is the copy than it was in the pre-computer past when photographic reproduction was the main source of copyright infringement. "The ability of so many people to gain access to [a copy of] an original work of art in this way, the ease with which images can be digitalized, manipulated, and then transferred, overshadows the question of right and wrong for a lot of people," says Paul Bassista, executive director of the Graphic Artists Guild. "It is now so easy to do, and the chances of getting caught relatively nil, that people believe that infringing on an artist's copyright is basically OK." Copyright is the right to make copies of one's own work. Under current law an artist is the copyright holder from the moment his or her artwork is completed, and it remains with the artist for 50 years after his or her death (heirs may monitor its use) even after the original artwork is sold, unless specifically waived by the artist. Laws in 10 states around the country (including California, Connecticut, Louisiana, Maine, Massachusetts, New Jersey, New Mexico, New York, Pennsylvania, and Rhode Island) a nd a recent amendment to the federal copyright law prohibit unauthorized alteration of original works of fine art. The laws also require that the artwork be attributed to the artist. In addition, statutes in California, Massachusetts, New York, and Oregon extend these rights to the work of commercial artists. The laws favor artists, yet copyright infringement is on the rise. Computer bulletin boards, which are filled with "shareware" that users can download (sending a few dollars to the creator of the program if they like), breed the idea that people can take whatever they want. Myrna Davis, who manages the Paul Davis Design Studio with her husband, says that she "met a young man who showed me his portfolio. The imagery was pretty good, since it belonged originally to a well-known commercial artist named Michael Schwab. This young man had been scanning in [other artists'] images without credit, changing things here and there, and he was stunned when I told him that he had violated the law, that he had violated someone's copyright. He just thought that once you put something in t he computer, it's all yours." Technological changes have been so rapid, Michael Whelan says, that "the law strains to deal with them. Artists can do everything correctly and still get ripped off, because it's hard to find the infringers, it's hard to go after them. What's more, it's not profitable to try and track down every single infringer." In addition, artists themselves are unaware in many cases that their rights may be violated or that a potential harm exists. Copper Gilmoth, an artist who uses computers and teaches at the University of Massachusetts at Amherst, reflected this attitude, noting that "appropriation is common in the art field. We can communicate with images now. Someone takes your images and deconstructs them. Someone takes my work and converts it in some way into their own work - that wouldn't worry me." That kind of "appropriation art," such as the work done by Mike Bidlo, Louise Lawler, and Philip Taaffe (who have used images by Pablo Picasso, Eliot Porter, and Bridget Riley, respectively), borrowed well-known pieces by famous artists. Such borrowing may be technically permissible under the legal doctrine known as "fair use," which allows an artist's images to be reproduced in the context of commentary. The use and alteration of images by Michael Whalen, Bill Lombardo, and other artists whose work is n ot world-famous presents a more straightforward case of copyright infringement. Digitalizing of artists' images is not entirely problematic. In fact, a growing number of fine and commercial artists regularly create on the computer. Some artists who create public works of art create designs that they scan into a computer in order to visualize the three-dimensional effect on the computer screen. Others who wish to show their art to a prospective art dealer scan their original works, printing them out on paper, as a replacement for small, hard-to-view photographic slides. Some museums have begun digitalizing works in their collections, enabling students and scholars to gain access to important pieces without having to travel hundreds or thousands of miles.