An investigation of boardroom leaks to the media by lame duck Hewlett Packard (HP) Chairwoman Patricia Dunn and other officials was more technologically sophisticated than originally thought, according to news reports.

The surveillance, assigned to private investigators last year, included planting tracing software on a reporter's computer that would enable messages to be traced as well as physical tracking of HP directors, according to a report in today's New York Times.

Investigators even attempted to drop email-based malware onto the PCs of those they were tracking to find out the leak's source, according to the Times' report.

News media had previously reported that investigators used "pretexting" techniques, pretending to be another person on the phone or email to gain information, to glean clues as to who was the leaker.

Reporters from CNET and BusinessWeek have been told by California authorities that they were targets of the investigation, according to the Times report.

Two board members have resigned following the incident.

HP said last week that Dunn will remain as chairman until January of next year, to be succeeded by Mark Hurd, company CEO and president.

In a statement issued last week, Dunn said she was resigning for the good of the company.

"The recent events that have taken place follow an important investigation that was required after the board sought to resolve the persistent disclosure of confidential information from within its ranks. These leaks had the potential to affect not only the stock price of HP, but also that of other publicly traded companies," she said. "Unfortunately, the investigation, which was conducted with third parties, included certain inappropriate techniques. These went beyond what we understood them to be, and I apologize that they were employed."

A HP representative could not be reached for comment today.

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