Is it possible to disassemble a dll?

Question

reverse engineering

I had a need to change one of the Windows dll. Is it real? As I understand it, for this you need to disassemble it, change it and assemble it. So: is there any protection on the win dll that will not allow this to be done? If this is still possible, I ask you to advise good disassemblers.

Answer 1

IDA Pro or ghidra , for example, if we talk about assembler.
If it is .NET, then ildasm, dotpeek, dnspy, ilspy
You will have to bypass all protections by hand, if any.