An investigation of the computer systems in several Interior Department (search) offices found numerous security flaws that threaten the department's overall computer security and must be fixed, according to an internal report.

Tests by the Interior Department's Office of the Inspector General found several bureaus and offices "still suffer from serious weaknesses in their security posture," Inspector General Earl Devaney (search) wrote in a Sept. 6 memo to Assistant Secretary Lynn Scarlett.

According to the report, obtained by The Associated Press on Thursday, investigators several times were able to masquerade as authorized users, roam the internal networks of some of the department's most sensitive computer systems and manipulate data. The tests were performed in phases beginning in November 2004.

But Devaney said the department has balked at fixing the system.

"Rather than simply accepting the results of our testing and promptly addressing the underlying vulnerabilities, the department and bureaus have, to date, expended considerable time and energy debating our findings, challenging our methodology and impugning the credentials and integrity of our staff and contractors," Devaney wrote.

"I do not wish to repeat this past experience," he added, suggesting the department work to fix the problem.

Interior Department spokesman Dan DuBray said the investigation was done as part of an internal effort to identify any "potential weaknesses or conceivable potential vulnerabilities."

The department's computer security has been challenged recently as part of a class-action lawsuit in which thousands of American Indians accuse the department of cheating them out of billions of dollars by mismanaging oil, gas, grazing, timber and other royalties from their land since 1887.

Plaintiffs have asked that a federal district court judge order Interior Secretary Gale Norton (search) to shut down the information technology systems to protect data.

DuBray said the department will continue to aggressively work to strengthen the computer systems, "which are now among the most intricately examined in all of government."