Seeing high CPU utilization? It may not be a fault with your computer.
Does your computer stutter when browsing certain websites? Does Windows Resource Monitor show high CPU utilization? Does your Mac's Activity Monitor show your CPU being overutilized? Typically, these symptoms would indicate a computer issue that would need troubleshooting but that may no longer be the case.
Your computer could have been hijacked to mine cryptocurrency. This is referred to as cryptojacking.
An increasing number of websites are including currency mining threads that use your processor to mine for their gain. More advertising networks are being hacked to include cryptocurrency miners and more malware than ever before is now using your computer to generate revenue rather than destroy or impact your data.
Forget Bitcoin, Monero, Litecoins, Dogecoins and Feathercoin are the new kids on the block and everyone wants a piece of them.
How does cryptocurrency mining work?
Bitcoin and other digital contexts are purely theoretical. Nothing exists, no paper money, no coins, no accounts, nothing. Everything is controlled by ledgers. Those ledgers are maintained by the companies that run the currency. To protect the currency, every transaction is encrypted and as you know, encryption is very resource intensive.
To help the system work, the processing of ledgers and transactions is farmed out to other machines, such as your PC to process. Your CPU will be given an encrypted transaction to process and the tools with which to do it. Your processor completes the calculation and sends the result to the central ledger.
In consensual cryptocurrency mining, you are then paid a fixed amount per transaction. You can run these transactions persistently to mine cryptocurrency.
The trouble is, websites and malicious code are using our computers to mine cryptocurrency without our knowledge. We pay for the electricity and contend with a slow computer but get none of the benefit from it. According to the piece from Adguard linked above, 500 million computers are being used to mine cryptocurrency without their owners even being aware.
Some of the websites that feature cryptojacking code profess no knowledge of it. Given the anonymous nature of cryptocurrency, we have to take their word for it.
How to tell us a website uses cryptojacking code
There is a quick and easy way to tell if a particular website uses cryptojacking code. If your CPU utilization spikes on a particular website or page, go to a different page. If utilization drops, it is a good indication that it is cryptojacking you. You could also shut down your browser as a double check.
How to prevent cryptojacking
While not as dangerous as malware or a virus, cryptojacking is still using your computer for someone else's gain. That is not acceptable and we need to do something about that.
Your first line of defense is an adblocker. As many types of cryptojacking code are served through infected ads, a good adblocker can stop them.
Next is a good quality malware scanner. Some types of cryptojacking code are delivered through malware and will not be detectable by an adblocker. If you see CPU utilization spike, run your scanner and remove anything it finds. If you still see high utilization, run your antivirus too, just in case.
Finally, there are some browser extensions emerging designed to block all manner of cryptojacking code. Extensions such as AntiMiner, NoCoin and MinerBlock are being tested to see if they can protect your computer.
Some websites are being up front about using cryptocurrency mining to help pay the bills. These sites we have no problem with and would suggest letting them use your computer to help keep the lights on. As more of us block ads to protect ourselves, this trend is likely to continue. If the website is honest, I see no issue with it. If they try to hide it, they deserve to be blocked.