Although the exact methods used to pirate the e-book are unclear, Glassbook, which made the King e-book reading software, said hackers were able to download the software from its site onto personal computers, where the encryption code was cracked.
The security breach likely will put the publishing industry on guard as it closely studies the potential for future Internet distribution of its content.
The e-book software is based on an open platform--the Electronic Book Exchange (EBX)--which is being developed by the Book Industry Study Group to limit e-book downloads to one copy per paying customer.
"One of the advantages of using an open specification like EBX is that the best security experts ... are able to collaborate" for strengthening the copyright of online content, Len Kawell, president of Waltham, Mass.-based Glassbook, said in a statement.
The electronic release of King's 66-page novella, "Riding the Bullet," created a splash in the publishing industry when it went on sale exclusively for Internet distribution earlier this month. More than 400,000 copies were downloaded in the first 24 hours, publisher Simon & Schuster said at the time.
"The excitement surrounding the Stephen King e-book brought out the best and worst of people on the Internet," Kawell said. "Unfortunately, there's no perfect copy-protection system."