NEW YORK — Think twice before you sign up for an online service using a fake name or e-mail address. You could be committing a federal crime.

Federal prosecutors turned to a novel interpretation of computer hacking law to indict a Missouri mother on charges connected to the suicide of a 13-year-old MySpace user.

Prosecutors alleged that by helping create a MySpace account in the name of someone who didn't exist, Lori Drew, 49, violated the News Corp.-owned site's terms of service and thus illegally accessed protected computers.

Legal experts warned Friday that such an interpretation could criminalize routine behavior on the Internet. After all, people regularly create accounts or post information under aliases for many legitimate reasons, including parody, spam avoidance and a desire to maintain their anonymity or privacy online or that of a child.

This new interpretation also gives a business contract the force of a law: Violations of a Web site's user agreement could now lead to criminal sanction, not just civil lawsuits or ejection from a site.

"I think the danger of applying a statute in this way is that it could have unintended consequences," said John Palfrey, a Harvard law professor who leads a MySpace-convened task force on Internet safety. "An application of a general statute like this might result in chilling a great deal of online speech and other freedom."

Drew, of O'Fallon, Mo., was indicted Thursday on charges of perpetrating a hoax on the popular online hangout MySpace. Prosecutors say Drew helped create a fake MySpace account to convince Megan Meier she was chatting with a nonexistent 16-year-old boy named Josh Evans. Megan hanged herself at home in October 2006, allegedly after receiving a dozen or more cruel messages, including one stating the world would be better off without her.

Drew, who has denied creating the account or sending messages to Megan, was indicted by a federal grand jury in Los Angeles on one count of conspiracy and three counts of accessing protected computers without authorization to get information used to inflict emotional distress on the girl.

Prosecutors argue that to access MySpace's servers, Drew first had to sign up for the service, which meant providing her name and date of birth and agreeing to abide by the site's terms of service.