The Japanese government in April'17 granted cryptocurrencies legal status as a means of settlement and in September'17 officially recognised 11 digital currencies exchanges. Crypto coins are not produced by any central authority such as RBI.These currencies like Monero and Bitcoin are created by computeer codes,solving complex math problems.The process requires huge amount of computing power. By incorporating piece of code into a website,cyber crooks use the laptop or mobile device of the website's visitors to 'mine' cryptocurrencies without their knowledge.The mining process can start quickly and quietly in the browser without anyone noticing.