A large coalition of publishing firms and related trade organizations has taken legal action against what the Association of American Publishers in Washington, D.C., described on Wednesday as "one of the largest pirate web-based businesses in the world."

At the request of 17 publishing companies in the United States, the United Kingdom and Germany, including HarperCollins, Oxford University Press and Macmillan, a Munich judge on Monday granted injunctions against illegal posting or sharing of online book files by two websites. Library.nu is alleged to have posted links to hundreds of thousands of illegal PDF copies of books since December 2010, Ed McCoyd, an attorney for the Association of American Publishers, told The Huffington Post. The majority of these uploads allegedly went through the website iFile.it, he said.

The coordinated legal action came after seven months of private investigation and was led by a German publishing association, Börsenverein des Deutschen Buchhandels, and the International Publishers Association.

The Munich court served Library.nu and iFile.it 17 separate injunctions, representing 10 book titles from each of the publishers. One of the injunctions, which The Huffington Post viewed in a translation from the original German, states that every Web link -- either on iFile.it or Library.nu -- leading to an illegal online copy of one of the named books would result in a fine of 250,000 euros or as much as six months in jail.

By Wednesday evening, iFile.it still listed PDFs of various popular works, though whether these works were named in any of the injunctions could not be verified. An iFile.it representative told The Huffington Post Wednesday that it is working hard to take down any potentially copyright-infringing files.

The joint action by the publishers is unusual. "We don't coordinate litigation against piracy sites as our normal course of action," McCoyd said. Instead publishers typically send what is called a "takedown notice" via lawyers and order a website company to take down copyrighted material, he said.

These two websites stood out, however. Rather than merely hosting a handful of book files, they were allegedly hosting and providing links to illegal PDF files of more than 400,000 books, including works by Salman Rushdie and Jonathan Franzen as well as many expensive textbooks.

The publishers and publishing associations hired Lausen Rechtsanwalte, a Germany law firm that specializes in tracking down and prosecuting copyright infringement, to find the parties responsible for the alleged book piracy. Since virtually all the files listed on Library.nu seemed to be hosted by iFile.it, the lawyers tried to find a connection between Library.nu and iFile.it, which is owned by DF Hosting based in Galway, Ireland, Ursula Feindor-Schmidt, a partner at Lausen Rechtsanwalte, said by phone from Germany.

But tracking down the ownership of Library.nu posed a challenge, according to Feindor-Schmidt. Library.nu appeared to be hosted in Ukraine but its Web address was registered on the small Pacific island of Niue, she said.

A representative from iFile.it who responded to an email request for comment (but wished not to be named) told The Huffington Post on Wednesday that Library.nu "has nothing to do with us."

But the lawyers acting for the ad-hoc publishing coalition think otherwise. "We thought they would be connected because of how the sites are constructed," Feindor-Schmidt said. "The registered addresses for the owners of both sites were also based in Ireland."

The owners of Library.nu had allegedly supplied false names and addresses when they had registered its Web domain name, according to Feindor-Schmidt. So the lawyers worked with the Irish National Federation Against Copyright Theft to hire private investigators to track down possible connections between the websites.

Then investigators found what they think was the real address for Library.nu, Feindor-Schmidt said. "We thought that it was strange that they were sitting around the corner in Galway from the owners of iFile.it," she said. "But we still couldn't prove a link."

In the end, a breakthrough came not from private investigators -- but from the Donate button on Library.nu, she said. "Users could give donations [to Library.nu] via PayPal in return for access to more files," Feindor-Schmidt said. "You then got an email stating that 'admin@library.nu has received your donation.' But then you got a real receipt from PayPal, stating the real name of the owner of the account. We received two different receipts with two real names."

The names on the receipts were Fidel Nunez and Irina Ivanova, Feindor-Schmidt said. The names correspond with those of the owners and directors of iFile.it, according to documents filed with the Irish Companies Registration Office. A judge accepted that a link had been proved between the sites and proceeded to grant joint injunctions, Feindor-Schmidt said.

On Wednesday, with the website Library.nu shut down, many Internet users were registering their disappointment on Reddit's online forums. Library.nu now redirects its visitors to Google Books. For its part, iFile.it was no longer allowing unregistered users to upload files on Wednesday.

As eReaders such as the Amazon Kindle and Barnes & Noble's Nook become more popular, online ebook piracy may continue to plague the industry. "Over the last two years, [ebook piracy] has grown tremendously," Feindor-Schmidt said.

"As a group, [publishers] want to show other sites that, where you have such a clear copyright infringement, it can't be accepted by the rights owners," she said.