Code segments are not writeble by default on Windows, like on any modern OS, but you can make any memory segment in your own process writable using VirtualProtect. That is not unique to Windows as well, on Linux you could achieve the same with mprotect.

As sibling notes, executable memory is not by default writable. If desired, you can also further disallow any executable memory to me allocated or modified by your process, even via the normal APIs, by calling SetProcessMitigationPolicy with ProcessDynamicCodePolicy.

https://learn.microsoft.com/en-us/windows/win32/api/processt...