BOSTON – Harvard Business School will reject 119 applicants who followed a hacker’s instructions and peeked into the school’s admission site to see if they had been accepted, the school’s dean said.

“This behavior is unethical at best – a serious breach of trust that cannot be countered by rationalization,” Kim Clark said in a statement yesterday. “Any applicant found to have done so will not be admitted to this school.”

An unknown hacker posted instructions last week on a BusinessWeek online message board on how to view the status of their applications. Applicants to at least six business schools took advantage of the instructions, although most got only blank screens.

Though some Harvard applicants did find information on their application status, school officials stressed that any decision wasn’t final until March 30.

Carnegie Mellon’s Tepper School of Business has already said it will reject those proven to have tried to peek at their files.

Other business schools, including MIT’s Sloan School of Management, Stanford’s Graduate School of Business, Duke’s Fuqua School of Business, and Dartmouth’s Tuck School of Business, have not said if they will reject applications.

All of the schools use ApplyYourself, an online application and notification program made by a Fairfax, Va., company. The company has said applicants could access only their own admissions records.

Some school administrators have said they’re reacting cautiously while they investigate specifically who tried to access the admissions files. A spouse or parent, for example, may have had access to the password and personal identification numbers given to an applicant.

But Clark told the Boston Globe that applicants were responsible for information that allowed them on the school’s Web site, regardless of who accessed it.

Sanford Kreisberg of Cambridge Essay Service, which helps students apply to elite American business schools, said he thought Harvard was overreacting.

He said some applicants may had inadvertently tried to access the files, without realizing they were looking for confidential information, after they were e-mailed directions from other students who had copied them from the BusinessWeek message board.

“What they did was stupid, but that’s all it was,” Mr. Kreisberg said. “This seems needlessly harsh and rigid.”