In early 2018, there is a shift from using malicious.exe for PDF, DOC attachments via emails to fileless techniques to deploy malware in the systems. Fileless malware also known as an invisible threat. It is hard to detect as it resides in system memory and Windows tools are hijacked to perform these attacks. So there is no interference of victim in these kinds of attacks.

https://www.geeksforgeeks.org/how-does-fileless-malware-make-its-way-to-computer/