Hackers attempted to hold computers at one Canadian university hostage for $28,500 on Tuesday, the Register reports. According to the CBC, Carleton University was hit with a ransomware attack from an unknown source.

"Any system accessible from the main network, that is Windows based, may have been compromised," the university stated on its website. Ransomware is a virus that keeps people from accessing their files unless they pay up.

A graduate student at Carleton says the hackers were asking for 39 bitcoin (about $28,500) to stop the attack. The university advised students to turn off their computers, stay off the university's Wi-Fi network, and not send any money to the hackers.

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Last June, the University of Calgary paid hackers $15,000 to get out of a ransomware attack, the Ottawa Citizen reports. Ransomware has also been used against hospitals and public transportation in the US and Europe.

Despite Carleton students having a hard time registering for things and getting their email, it doesn't appear the university is prepared to pay the ransom, with the Register reporting the school may be turning to its backups to restore things.

Public Safety Canada says that's a good thing, as ransom payment doesn't guarantee you'll get your files back and encourages further attacks. A spokesperson for Carleton University tells the Register "it's hard to say at this point when the problem will be sorted out." ("Creepy" search engine taps into private webcams.)

This article originally appeared on Newser: Hackers Holding College's Computers for Ransom