Cryptocurrency mining was one of the biggest trends in technology in 2017 yet as is often the case when there's a surge in interest in something, it attracts its fair share of bad eggs.

According to Symantec's latest cyber security threat guide, detections of coinminers on endpoint computers surged by 8,500 percent in 2017. Activity was flat through most of the year but skyrocketed in the final months of 2017, correlating with spikes in cryptocurrency prices at the time.

As Symantec highlights, some cyber criminals use coinminers to steal victims' computer processing power to mine cryptocurrencies. It can be trivially easy to cryptojack a machine - potentially only requiring a few lines of code - and criminals can often fly under the radar due in part to the anonymous nature of cryptocurrencies and the fact that victims may not even realize their machines have been compromised (computer slowdowns are often attributed to other issues or even old age).

In addition to slowing down a machine and potentially hampering productivity, cryptojackers are essentially stealing electricity from their victims. Worse yet, excessive heat generated by mining can easily ruin hardware or cause mobile phone batteries to overheat.

Symantec says the threat has largely been limited to computers and mobile phones but as coinminers evolve, cyber criminals may increasingly target IoT devices. Individually, such devices aren't very capable and thus, won't generate any significant gains but when you've got an army of them at your disposal, it can be quite profitable. There's power in numbers, after all.

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