Because mining cryptocurrency involves a lot of computing power, many started "borrowing" others' resources.
Openload, Streamango, Rapidvideo and OnlineVideoConverter, which are four popular video-streaming service, have been found to do cryptojacking.
They allegedly load mining software on to visitors’ computers, making them generate tokens for the bitcoin-like cryptocurrency Monero, according to security firm Adguard.
With almost a billion visitors visit those four popular video websites each month, they all have been turned into miners while watching videos.
"We came across several very popular websites that secretly use the resources of users’ devices for cryptocurrency mining," said Andrey Meshkov, co-founder of Adguard.
Monero is popular for being mined this way, unlike Bitcoin, because the cryptocurrency is more readily lends itself to behind-the-scenes operation such as cryptojacking. Cryptojacking is a way to mine cryptocurrencies by loading a mining program to the users' browsers when the video player is downloaded and ready to stream the video.
"The popularity of cryptojacking has grown with alarming speed. Just think about it; we are talking about billions of visits, and it has been just a few months since this problem first appeared," AdGuard concludes. "It's like an epidemic, and it is unclear when it will stop or even slow down."
Mining Monero doesn't involve heavily specified application-specific integrated circuits (ASICs), like Bitcoin. Therefore, mining Monero can be done with practically any CPU or GPU.
And because Monero is also untraceable and faster to mine and confirm transactions, it's easier for websites to get away with cryptojacking.
Visitors of the four website aren't notified, and so they aren't aware that their computer is 'forced' to mine Monero for them.
The only clue that most users would be experiencing, is their computers running a bit slower than usual when playing videos. They will notice their computers performing more slowly than usual as the mining software hogs the computer's resources, taking about 60 percent or more of its computational power.
"The total monthly earnings from [this] cryptojacking, taking into account the current Monero rate, can reach $326,000. These are simply outrageous figures," continued Meshkov.
Most of the popular websites that are getting on this trend appear to be streaming related. In case of Openload, for example, users don’t need to visit the site itself to be a victim since it’s often used as an embedded video player on other resources. Because some other websites may aggregate entertainment content link from different players, Openload being one of the most popular to serve this service, is able to load its player, including the mining script as well.
Therefore, the streaming services can spread their reach and generate revenue although people aren't visiting their website. While ad-blockers can stop cryptocurrency mining from working, many users are still at risk.
This isn’t the first time sites have been accused of using visitors’ computers to mine cryptocurrency.
Back in September 2017, torrent search website The Pirate Bay came under fire for using a cryptocurrency mining scheme without user consent. Users worried that malvertising may be at play, but the website's operators said it was just doing an experiment to see whether cryptocurrency mining could provide the revenue required to run The Pirate Bay without ads.