Code injection techniques (T1055 from MITRE[1]) is a common technique these days. It’s a nice way for an attacker to hide malicious code into a legit process. A deviation of this technique is called “Process Hollowing”[2] where code of the legit suspended process is wiped and replaced by malicious code. Code injection is performed by calling Microsoft API calls like: VirtualAllocEx(), NtUnmapViewOfSecrio(), WriteProcessMemory(), ... (they are many others available)