After four years of altering grades using credentials gained with keylogger equipment installed on professors' keyboards, three Purdue University students were finally busted when one of those professors complained that one of his passwords mysteriously changed.

According to court documents made public last week, the first grade change happened in December 2008, while the last occurred in December 2012. Officials at the Indiana university realized something was amiss when a professor requested that his university computer account password be reset twice, once in November and once in December, because it had been changed it without his permission.

After analyzing logs, Curt Jansen, network security analyst for the university, connected the password changes to Mitsutoshi Shirasaki, 24. He determined that Shirasaki, an aeronautics and astronautics major, had logged into the professor's account and changed his grade in a course from a "C" to a "B." Further analysis showed that "grades in four of Shirasaki's other classes from the fall semester of 2012 were changed to a higher grade."

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When Purdue University police officials interviewed Shirasaki, the scheme came to light. The student claimed that he learned how to access professors' accounts from another student, Roy Chaoran Sun, 24, who graduated from Purdue with a bachelor’s degree in electrical engineering in May 2010.

The students picked the locks on professors' offices and tampered with their keyboards, cutting and reconnecting wires with electrical tape in order to attach keylogging devices. In some cases, they just plain switched out keyboards for ones they'd already modified.

Later, the students revisited the offices and collect the keylogging devices, from which they would pull the credentials necessary to access their professors' university accounts — and change grades. A third accomplice, nuclear engineering major Sujay Sharma, 24, occasionally acted as a lookout during the office break-ins. Only one of his grades was changed, but he is accused of accessing exam materials.

The Journal & Courier reports that the men have been charged with "multiple felonies and misdemeanors — among them, conspiracy to commit computer tampering, conspiracy to commit burglary and conspiracy to commit computer trespass." Sharma and Sun have been arrested. Shirasaki is presently in Japan.

Sun graduated from Purdue in May 2010, but according to the Journal & Courier, his degree is being reviewed and "a hearing will be held that will give Sun an opportunity to respond to the allegations." (Purdue recently adopted a process for degree revocation.) Shirasaki and Sharma most recently were seniors at Purdue, but they are no longer students.

Authorities, in the meantime, have discovered a keylogging device as well as lockpicking tools in Shirasaki's apartment. They've also recovered a laptop, several computer hard drives, additional keylogging devices, and more lockpicking tools discarded by the students once they realized they might be busted.

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