The term "cryptojacking" refers to malware infections that result in someone's computer (phone, tablet, laptop, desktop computer) running cryptocurrency mining software without the user's knowledge.
According to McAfee Labs, which is the Advanced Threat Research division of McAfee, it detected over 2.9 million cases of "coin miner malware" infections in Q1 2018 compared with almost 400,000 such cases in Q4 2017.
The report notes that
"This suggests that cybercriminals are warming to the prospect of monetizing infections of user systems without prompting victims to make payments, as is the case with popular ransomware schemes. Compared with well-established cybercrime activities such as data theft and ransomware, cryptojacking is simpler, more straightforward, and less risky. All criminals must do is infect millions of systems and start monetizing the attack by mining for cryptocurrencies on victims’ systems. There are no middlemen, there are no fraud schemes, and there are no victims who need to be prompted to pay and who, potentially, may back up their systems in advance and refuse to pay."
"Bad actors demonstrated a remarkable level of technical agility and innovation in tools and tactics. Criminals continued to adopt cryptocurrency mining to easily monetize their criminal activity.”
“Cybercriminals will gravitate to criminal activity that maximizes their profit... In recent quarters we have seen a shift to ransomware from data-theft, as ransomware is a more efficient crime. With the rise in value of cryptocurrencies, the market forces are driving criminals to crypto-jacking and the theft of cryptocurrency. Cybercrime is a business, and market forces will continue to shape where adversaries focus their efforts.”