The Proctor school district was hit by a malicious computer software "ransomware" attack last weekend.

Student data and payroll information were not affected, said superintendent John Engelking, but some information kept in Microsoft Word files has been locked away by the hacker. Only computers at the middle and high school were affected, and only those that were left on over the weekend.

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The district has not yet notified authorities, but it has hired a forensic data company to deal with the hacker, who hasn't yet requested an amount of money. The district won't pay it, Engelking said. The hired company's job is to find "patient zero," or the computer that initially was attacked, and write a code to release the data.

Engelking said much of school and district operations is done through Google, and that wasn't affected.

What has been locked away are things such as curriculum files, Engelking said, creating inconveniences for teachers. He wasn't sure when the issue would be resolved.

Proctor's attack wasn't as debilitating as the one the Cloquet school district experienced in 2016. That resulted in the closure of school and a demand for $6,000 in bitcoin, a digital currency. It, too, did not pay the ransom. The malware corrupted and encrypted most of the district's servers, disrupting email, phones, the school bell system and SmartBoards.

Ransomware attacks have become an increasingly common way to hack into systems. Media companies, hospitals and businesses have been targeted in recent years.

Mecklenburg County, N.C., which includes the city of Charlotte, suffered a ransomware attack earlier this month in which many government files and data servers were encrypted or locked, leading to what one county official described as a "crisis."

The hacker or hackers demanded the equivalent of about $23,000 in bitcoin, but the county refused to pay, choosing instead to restore files from backup copies and rebuild its systems.

That attack happened after an employee opened a malicious "phishing" email and accessed an attached file that unleashed a widespread problem inside the county's network of computers and information technology. In the wake of the attack, county officials limited employees' ability to open some email attachments.

The Charlotte (N.C.) Observer contributed to this report.