What is mercenary spyware?

Could you please elaborate on the concept of mercenary spyware? I'm curious to understand what it entails and how it differs from other forms of malware. Specifically, how does it operate, who are its primary targets, and what are the potential consequences of being infected by such spyware? Additionally, are there any specific industries or sectors that are more vulnerable to mercenary spyware attacks, and what measures can be taken to prevent or mitigate the risks associated with it?