When he assigned a paper on 20th century theater, Carnegie Mellon University assistant professor Michael Chemers was surprised at what a student submitted.

A sophomore turned in a paper on Antonin Artaud, a complex playwright and director the class had never discussed, written completely outside the skill level the student had shown in class.

So Dr. Chemers confronted the student. When the student stood by his paper, Dr. Chemers asked him to explain how he arrived at the thesis he wrote.

The student instead explained that he bought the paper online.

While the Internet hasn't created plagiarism, it has contributed new opportunities for violating professors' trust.

"It's so much easier to just take things off the Web," said Deborah Rubin, director of the social work program at Chatham University.

In national surveys of more than 80,000 college students conducted from 2002 until this spring, nearly half admitted they cheated via the Internet, according to researcher Donald McCabe, founder of the Center for Academic Integrity, a consortium based at Clemson University.

It's unclear how many of them would have cheated anyway. Dr. McCabe, who is also a professor of management and global business at Rutgers University, said other survey questions showed as many as 42 percent said they plagiarized from written sources, not necessarily the Internet.

The ways included fabricating research citations; submitting work that someone else, such as a peer, has written; cutting and pasting from written sources; and submitting a paper taken all or most from another written source.

But Dr. McCabe, who has researched cheating since 1990, believes the volume of cheating has increased.

"It's just made it easier so the people who are doing it are doing it more often," Dr. McCabe said.

Plagiarism hits at the heart of education.

"The entire relationship between the professor and the student is built on trust, that you're honestly submitting your work, and I'm honestly grading it," Dr. Chemers said. "When you violate that, there's nothing left."

Dr. Chemers has other war stories to tell about blatant plagiarism.

While teaching at Shoreline Community College in Seattle in 2002, he confronted a student who copied and pasted information from a Web site word-for-word into a new document and turned it in as her own research paper.

That student begged for forgiveness and asked for a second chance. This time, she vowed, she would write a paper on plagiarism.

She plagiarized that one, too, copying whole portions from another online source.

Dr. Chemers' father, a professor at University of California-Santa Cruz, once encountered one student who bought a paper from a paper mill and submitted it as his own. That plagiarism was easy to catch: It was an article the professor himself had written in an academic journal.

With students now conditioned to performing their research online, Dr. Chemers said they copy phrases, sentences and sometimes paragraphs word-for-word from Internet sources. Even when they attempt to paraphrase, students often neglect to cite the source, and sometimes purchase entire papers from online term-paper mills.

Dr. McCabe believes his cheating survey may understate the problem. The more serious the offense, he said, the less likely students are willing to admit they've done it. Likewise, those who did voluntarily respond -- only 15 percent of all possible students polled -- tend to minimize what they've done, he said.

And he said some students may not consider it cheating.

"When you read the comments students provide, their cheating is everyone else's fault but theirs," Dr. McCabe said. "Their parents put too much pressure on them, or the faculty does a lousy job teaching their courses or the assignments are too hard. For a lot of students, they've figured out a way to justify it."

In their experience, Dr. Rubin and Robert Alexander, a professor of English and the director of the university writing program at Point Park University, have both found that many students don't consider copying and pasting sentences to be plagiarism. Nor do they find a problem with omitting citations for the sources of their primary intellectual arguments.

Dr. Chemers has found that, for some students, the monetary transaction of purchasing a paper online makes it seem legitimate.

In his 35 years of teaching, Dr. Alexander has seen a slight rise in issues of academic integrity with the onset of the Internet. While professors tell him about several cases of plagiarism every semester, often in freshman composition classes, he's not especially concerned.

"It's not an extensive problem," he said.

Some students may be deterred by the threat of punishment. At most local schools, online plagiarism warrants failing the assignment, failing the course and sometimes expulsion. Dr. Chemers' Artaud scholar was expelled.

"But for every one that comes to official status, you have to figure there are 10 that don't," Dr. Chemers said.

Many cases, he said, are handled between the professor and the student because the process of addressing discipline on an institutional level can be a hassle.

Plagiarism is an international problem, according to a report released this summer by UNESCO, the United Nations' education-and-science agency. The report -- "Corrupt Schools, Corrupt Universities: What Can Be Done?" -- cites a case at an Australian-run university in Malaysia in which 15 cases of plagiarism were overlooked because the university was "concerned with losing revenue from off-shore students."

But how do professors know when students have turned in work that's not altogether theirs in the first place?

Just as students are becoming more comfortable in using the Internet, so are professors. Faculty at universities throughout Pittsburgh reported using the Internet to catch academic dishonesty in two ways: using Google to search for suspicious lines or phrases in assignments and submitting students' papers to online companies such as www.turnitin.com.

At www.turnitin.com, the company puts each document through a search that includes current and archived Web sites, a database of student papers previously submitted to the company, and commercial databases of periodicals and journal articles.

The report then tracks each passage of the paper, showing the possible source and clearly identifying unoriginal material.

But many times, professors don't even need an originality report.

"Sometimes it's easy to spot because you're used to students' writing style," Dr. Rubin said. Like many professors, she gives in-class assignments first to gauge students' writing abilities.

Dr. Chemers said he is not only familiar with all of the published material in his field, but he also knows many of the authors personally.

While some American students have a hard time understanding what plagiarism is, it's even more difficult for international students.

Toni Carbo, a professor in the School of Information Sciences and the Graduate School of Public and International Affairs at the University of Pittsburgh, has found that norms about information sharing are very different among cultures.

Dr. Carbo, who teaches information ethics, said in some Asian and African cultures, for example, academics are part of an intellectual community in which sharing information without attribution is accepted.

Some students from Asian countries, who come from a tradition of not using footnotes or quotation marks in their research reports, know to list sources in the bibliography but learn other ways to attribute information when they get here, Dr. Carbo said. Some African students have different concepts of privacy than Americans, she said.

The Internet also raises more issues for academic integrity in higher education. Some students have difficulty telling an accurate site from an inaccurate one.

In a theater history class, Dr. Chemers had a student who submitted a paper on ancient Roman theater citing the proletariat as the cause of the Roman Empire's fall.

There's just one problem, Dr. Chemers said. There was no proletariat in ancient Rome. The student admitted he found the historically inaccurate information from someone's personal Web site.

Local faculty agree education is the key to stopping students from using the Internet dishonestly.

Faculty point to the importance of using course syllabi to explain both what plagiarism is and what repercussions are for students who plagiarize.

They also teach classes on how to use Internet sources responsibly, both finding and citing sources.

Dr. Rubin gives her students a topic relevant to social work -- such as abortion and poverty -- and assigns them to look up sites on the topic and evaluate the quality of those sites in comparison with scholarly journals.

Dr. Chemers, meanwhile, devotes a class each semester to teaching his students how to find which sites are credible, such as the institution that hosts the site and the academic sources the site uses in footnotes.

At Pitt, faculty are also taught how to evaluate sites through a series of workshops and training sessions offered through the Center for Instructional Development and Distance Education.

Additionally, Dr. Rubin and Dr. Chemers both give specific assignments that are too nuanced or personal to be plagiarized, while Dr. Carbo requires her students to submit multiple drafts of papers, making it easier to filter out cut-and-paste phrases.

"[Cheating] is like a chronic disease that you can't cure," Dr. Alexander said. "But you can learn how to manage it and make it as least harmful as possible."