Cryptojacking is an illegal form of crypto mining where cybercriminals hijack miners' devices to mine cryptocurrencies. Cryptojacking occurs when cybercriminals hack into a computer without the owner’s knowledge or consent and install crypto software. These cybercriminals can then break into crypto wallets or use the processing power to mine for cryptocurrency. 

Thus, cryptojackers can earn cryptocurrencies without incurring expenditure for any hardware and overhead costs such as electricity bills. Although there are crackdowns by law enforcement on cryptojacking, hackers are still at large to take advantage of unsuspecting victims. 
There are mainly two ways for hackers to hijack your devices:

• Sending malicious links in emails
• Infecting a website or online ad with viruses

Users have to always be careful when visiting websites and clicking on random links sent by other people.