: Many security tools focus on scanning files on disk. By living only in RAM , shellcode-based payloads can bypass traditional static signature detection.
Further reading (tools to search)
The most reliable way to convert an existing EXE into shellcode is using tools that wrap the EXE in a "loader stub." This stub acts as a mini-OS loader to handle memory allocation and dependency resolution.
Writing this loader from scratch is tedious. Fortunately, the security community has developed tools to automate this process.