What knowledge do you need to have to write your own "Anti-Virus"?

Question

reverse engineering

What knowledge do you need to have for this?
There are only 2 questions (But you can also add something useful)
1. What language?
2. What is the best book on reverse engineering?
I just want to learn how to do it, I don’t want to write my own Kaspersky or something like that, I just want to find where to go

Answer 1

Learn the architecture of the operating system
Learn how to write your own viruses
learn English and read English-language forums / hangouts

Answer 2

a modern virus is a huge complex of programs that perform many functions - finding vulnerabilities, hacking, infecting, fighting antiviruses, performing a "payload"
to learn how to write antiviruses - you need to learn how to write viruses.
language - C / assembler (although there are viruses for Word)
reverse engineering ... - study assembler again, take a disassembler, experiment. learn how to simply "break" programs - for example, disable protection, checks, etc.
it's interesting, but it takes a lot of time.