A disgruntled software programmer who "harvested" colleagues' passwords before he quit pleaded guilty Friday to hacking into his former employer's computer system in a "digital retaliation campaign," said the U.S. attorney's office for Long Island.

Michael Meneses, 43, a former Smithtown resident, had been upset at being passed over for promotions at a Long Island-based company that makes high-voltage power supplies, officials said.

The hacker, who worked there since 2008 as a software programmer and system manager, got his colleagues' logins and passwords before quitting in January 2012, authorities said.

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In the weeks that followed, he logged in to look at emails, interfered with work or purchase orders, changed the calendar, deleted part of a code in a software program and warned off at least one candidate for his old job, officials said. He was arrested in May 2013.

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"The defendant used his programming knowledge to hack into the computer network of his former employer and launch a campaign of digital retaliation," said U.S. Attorney Loretta E. Lynch in a statement. "The threat posed by disgruntled and former employees is serious, and we will continue to work closely with our law enforcement and private sector partners to vigorously prosecute insider attacks."

At his sentencing on computer-related fraud, scheduled for July 7 at Central Islip federal court, Meneses faces up to 10 years in prison, as well as restitution and a fine.

His attorney could not be reached Friday.