To be a malware analyst, the minimum knowledge typically needed is:
- Assembly language
- Operating system internals
- Deobfuscation and anti-anti-debugging techniques
Most of the things you'll need to know you'll learn along the way. For example, you may come across a malware sample that exploits Adobe Flash player. This will give you the opportunity to learn about the SWF file format, ActionScript source and bytecode, etc.