The author, who is expected to release the next instalment of the Potter saga in July, claimed that fans were being targeted by an online scam asking for money in return for early copies.
"You should never trust any Harry Potter ebooks offered for download on the internet or any other p2p/filetrading networks," said Rowling in a statement on her website. "Setting aside the fact that these books are illegal, they may infect your computer with viruses, leave you vulnerable to the dangers of hacking and/or credit card fraud and may also contain content that has nothing to do with Harry Potter, to say the least."
The email scam attempts to lure fans waiting for Harry Potter and the Half-Blood Prince by asserting the sender has an early copy of the book available to anyone willing to give over their card details. Rowling maintains none of her books have ever been legally sold in digital form.
"Please, please protect yourselves, your computers and your credit cards," she said.
Phishing scams hit the headlines recently as a result of the Asian Tsunami. Almost instantly a number of email-borne messages appeared in inboxes claiming to offer the chance to aid victims.