The NSW man was found to have searched visa applications by nationality and processed them accordingly, the Australian Law Enforcement Integrity Commission confirmed on Thursday.

The four-year investigation showed the visa processing officer had chosen Macedonian nationals, processing more than one-third of the student visa applications originating from the country in that period.

It found evidence that the man had also told other officers how to process self-selected visa applications, which is against department policy, to avoid being detected in what he described as "cherry-picking".

The investigation was prompted after an allegation was made that a Serbian national employed at the Australian Embassy in its capital, Belgrade, was approving visas based on false information for money.

The investigation did not find any evidence to support the allegation, but instead uncovered the NSW visa officer's misconduct.

Integrity Commissioner Jaala Hinchcliffe said the evidence showed he had acted in an intentionally dishonest manner.

"This demonstrates that [the visa officer] knew that processing applications in this way was against policy and therefore needed to avoid detection when engaging in this conduct," she said.

"This shows [the visa officer] was being intentionally dishonest when engaging in this conduct."

The officer was suspended at the beginning of the commission's investigation in 2017, and has since resigned from the role.

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It comes after the law enforcement watchdog warned federal police and border officers to stay alert to grooming practices by criminal organisations, in a crackdown prompted by a rise in possible cases.

The integrity commission's annual report said some officers could unwittingly be targeted by someone seeking to exploit their insights into operations.

"Law enforcement officials were deliberately targeted by commercial and criminal entities with a view to corrupting them to secure undue advantages," the report said.

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