University campuses aren't just producing new college graduates. They're also churning out lots of cryptocurrency.

Security researchers at Cisco have been monitoring cryptocurrency mining across different industry verticals, and college campuses are the second biggest miners of virtual currencies, at about 22 percent.

This is probably due to opportunistic students who are creating mining rigs in their dorm rooms, according to Cisco threat researcher Austin McBride. "You leave [the mining rig] running in your dorm room for four years, you walk out of college with a big chunk of change," he said during a Monday talk at RSA.

The students are likely mining the cryptocurrency to capitalize on the free electricity they receive from the university campus. "So you can run your mining rig in your dorm or school library and not worry about those costs eating into your mining profitability," McBride told PCMag in an email.

Cisco noticed the mining through the company's Umbrella security product, which can monitor a client's network connections to block out malicious activity, including suspected crytocurrency mining on the internet. Umbrella currently processes 180 million Domain Name Server requests each day.

McBride said campus cryptocurrency mining is "quite distributed," which indicates that many students are mining across dorm rooms. But not all the cryptocurrency mining is done by students. Hackers have also been infecting vulnerable computers with malware that secretly uses the hardware to mine virtual currency.

"Mining difficulty for a lot of coins is very high right now—which means it costs more for electricity and internet than the profit you can produce from mining those coins," he added. "If you don't have to pay for those costs, then you are in a really good spot for making money on the university's dime."

So it's not surprising that the No. 1 biggest miner of virtual currencies is the energy and utilities sector, according to Cisco. McBride speculates it's because these companies are running old computers that can be easily infected with mining malware.

"Some of the systems that run our grids and other utilities are purpose build and do not get software and hardware updates as frequently as a Mac or PC would," he added. "So, there is more of a potential for vulnerabilities being unpatched for some time and this makes it an attractive target."

The mining itself may seem like a harmless nuisance. But prolonged mining can hamper affected companies and organizations by increasing electricity bills and putting strain on the hardware. Getting infected with mining malware can also potentially open the door for other strain of malicious code. As a result, affected businesses should be on watch for unsanctioned mining.

Although the cryptocurrency market has plummeted since its record high in Decemeber 2017, mining for virtual currencies is actually growing, according to Cisco's findings. For instance, mining-related internet traffic increased by over 19 times in the last nine months of 2018.