Process injection is a common technique used by malware to cover their tracks. What looks more legit than a process called "notepad.exe" or "explorer.exe"? They are multiple ways to perform process injection, one of them is called "Process Hollowing" (T1055/012/)[1]. When I'm teaching FOR610, students are often surprised that it's a feature of the operating system, so, by default, not malicious. Microsoft offers all the required API calls to perform this. Some legit applications use many process injection techniques like your best antivirus or EDR solution!