Image caption Many students cross the line under pressure

A German minister has resigned after copying huge chunks of his doctoral thesis, while the London School of Economics is probing whether Colonel Gaddafi's son lifted chunks and used a ghost writer for his own. So is plagiarism out of control?

It's been a bad week for honest educational endeavour.

The German defence minister has stepped down after being stripped of his 2006 university doctorate thesis for copying large parts of it. The University of Bayreuth had decided Karl-Theodor zu Guttenberg had lifted whole sections without attribution.

And the LSE is looking into allegations that Colonel Gaddafi's son, Saif al-Islam plagiarised his PhD thesis.

These are very high-profile cases, but in the worlds of academia and publishing, the issue of plagiarism has been a problem for many years.

The internet now offers students unparalleled opportunities to duplicate and to fabricate, says Jude Carroll, of Oxford Brookes University, the author of A Handbook for Deterring Plagiarism in Higher Education.

The pronouns go from single to plural, a sentence is cut off in the middle, or a strange reference to Australia appears Jude Carroll, On the tell-tale signs

"Google gave students access to a much greater library of texts," she says. "The opportunities to harvest material have increased."

Where once plagiarism might have involved extensive reading and copying by hand, now it can be as easy as Googling the subject matter and hitting Ctrl+C, Ctrl+V. From Wikipedia and other free sources to academic journal databases like JSTOR, there's a treasure trove for the would-be cheat.

"The poet Byron never let people come into his library because he didn't want people to see what he was copying from," Carroll notes, referencing a story from Robert Macfarlane in the Times Higher Education.

"The difference now is that we can all copy each other's libraries."

Plagiarism has been with us for as long as the written word. From the classical Greek playwrights, to Dr Martin Luther King, even the greatest of historical figures have been tainted by scandal.

But over the last decade, academics have spoken out with increasing exasperation over the tide of students using everything from Wikipedia to bespoke essay writing services in pursuit of easy high grades. Universities are involved in a cat and mouse game to stop the plagiarists in their tracks.

In the UK, 98% of universities now use a computer programme called Turnitin to analyse suspicious essays, the company that provides it says.

The software scans text for passages which match a database of 155 million student papers, 110 million documents, and 14 billion web pages. Back in 2006/7, more than 600,000 essays were checked in this way in the UK. By last year, that figure leapt to three million.

Image caption The German minister has been mocked as zu Googleberg for his extensive plagiarism

But of course, a matching passage does not necessarily indicate a plagiarist. A scholarly essay is traditionally embroidered with well-chosen quotes and references.

"The software is not a silver bullet," says Barry Calvert, of iParadigms, the creators of Turnitin. "It still takes a human to detect a cheat."

Often, what appears to be fraud is simply a student who is unable to write proper footnotes, or who forgets to accredit properly.

In cases of genuine deceit, suspicion is more often aroused by a lecturer reading over the essay, and noticing "something which just doesn't feel right", says Carroll.

"You might notice a sudden variation - from good language to bad, from academic tone to journalistic tone. The pronouns go from single to plural, a sentence is cut off in the middle, or a strange reference to Australia appears."

And who are the plagiarisers? Many are first year undergraduates who copy and paste simply because they have not been given appropriate instructions on how to write an essay, says Dr John Olsson, of the Forensic Linguistics Institute.

"You're just out of school and suddenly you're being asked to write 3,000 words on a subject by Monday. It's a daunting task," he says.

Plagiarism allegations Kaavya Viswanathan: Young adult novelist accidentally "internalised" somebody else's novel

US vice-president Joe Biden: Accused of plagiarism in law article and of taking line in speech from Neil Kinnock

Martin Luther King: Posthumously accused of plagiarism over doctoral thesis

"I've handled cases where students were thrown off courses for paraphrasing a couple of paragraphs."

But it's not just a problem in academia. Journalism is rife with episodes of alleged plagiarism.

New York Times columnist Maureen Dowd admitted using a paragraph virtually word-for-word from blogger Josh Marshall without attribution. Dowd, a Pulitzer Prize winner, said her mistake was unintentional, claiming she had heard the line from a friend.

And in the world of publishing, agents and editors must be on their guard for a potentially commercially damaging episode of lifting.

In publishing, incidents of apparent plagiarism have increased a lot in recent years, says literary agent Mark Lucas, due to such widespread access to electronically transmitted data.

But while detecting plagiarism is increasingly difficult, the rules remain the same, he says.

"Our agreement with our clients is that they undertake to us that plagiarism is off limits, as it always has been," he says.

"The line that exists between something unique and original and something that is clearly derivative is a relatively thick one still."

But there are some who think a more generous approach should be taken to lesser offenders in the digital age.

Instead of coming down hard, first year students should be allowed a little leeway, "to find their own voice", Olsson says. But for postgraduate students, like zu Guttenberg and Gaddafi, there is no excuse.

'Mixing' not copying

There are some who sense a generational shift in what is and isn't acceptable.

Kaavya Viswanathan, whose 2006 young adult novel was the subject of extensive and wide-ranging allegations of plagiarism, detailed at great length on Wikipedia, came a cropper, and faced the wrath of her publisher.

But more recently Helene Hegemann, a 17-year-old German author, defended herself against allegations of wholesale lifting by reference to "mixing" and insisting: "There's no such thing as originality anyway, just authenticity."

It's prompted discussions about the long tradition of authors drawing on other people's work. Some would see a shifting into a more modern tendency to lift other's stuff because of a failure to recognise long-held notions about ownership of ideas.

But academics want to hold the line. Advances in technology do not mean we should redefine our idea of what plagiarism is, says Olsson.

"I don't think we should change our standards. That would be very dangerous in higher education," he says.

Carroll agrees: "Being 'original' does not mean having novel ideas never before expressed by a human. It simply means doing the work for yourself."

Additional reporting by James Morgan and Brigitt Hauck