Cypto currency mining malware, which embeds itself in online Ads made a comeback last week after several malicious Ads showed up on Youtube. Once hackers gain access to your computer through malicious Ads, they steal your computing power and electricity, which they use to mine cryptocurrencies without your knowledge. The process known as drive-by mining, or crypto jacking, is gaining notoriety as the latest cyber security threat facing the crypto currency industry.

Cryptojackers profit by harnessing the computing power of everyday computers connected to the internet. Because of the hefty rewards involved, crypto jacking is increasingly becoming a common problem. Going by last week’s episode where millions of Youtube users were affected, crypto jacking could evolve into one of the biggest cyber security threats in coming days.

Youtube’s attack came into the limelight after users started to complain on social media. Following the complaints, Google, which owns Youtube, confirmed that its Ads platform had been attacked, adding that it removed the offending Ads in a couple of hours. According to a report generated by TrendMicro, a cyber security firm, attackers are believed to have used Google’s DoubleClick Ad service to plant malicious code on Youtube. The cyber attack, which mostly targeted Youtube users in Taiwan, Japan, France, Italy and Spain, is believed to have affected 55% of businesses worldwide.

Data from TrendMicro shows that over 90% of all Youtube Ads were affected by last week’s attack, which was utilizing a JavaScript code from Coinhive. For the last few years, Coinhive has dubiously made a name as a notorious crypto currency miner which allows hackers to use other people’s computers to mine crypto coins, without the user’s consent or knowledge. In YouTube’s case, private miner was deployed by hackers to mine crypto currencies from the remaining 10% of PCs. When crypto jacking happens, user PCs become extremely slow as most of their computing power is directed to crypto-mining.

In September last year, cybersecurity experts investigating crypto jacking found thousands of video streaming and file sharing websites which were hosting malicious mining software. And Coinhive is not the only culprit, according to various reports. There are many other similar malicious software similar to Coinhive which are as intrusive. To stay safe, cyber security experts recommend the use of third party antivirus software, in addition to installing an Ad Blocker.