Very, very hard. The equipment to do this isn't trivial but not complicated and largely available in biohacker spaces or on ebay even. That assumes you know how

Very, very hard. The equipment to do this isn't trivial but not complicated and largely available in biohacker spaces or on ebay even. That assumes you know how to make a super virus though, that's very very hard, we don't really know. If you wanted to recreate an existing virus you could, but DNA synthesis companies watch for those sequences so you'd likely be reported to the FBI for trying. EDIT: I should clarify, this is for human-infectious viruses. Human viruses are hard to grow because they require human cells or higher-organism cells to reproduce. That sort of tissue culture is very hard to do. Doing the mutation screening etc. is also quite hard to do in those viruses. CRISPR helps a bit, but there's a whole lot else that's still quite technically and biologically hard.