I don't know when you were a virus writer (the heyday of the virus writers I knew was the mid-1990s, and the virus writers I was aware of post-2000 had more knowledge of WinAPI than of x86), but: the state of the art for disassembly and reverse engineering has progressed dramatically in the past 10 years.
In particular, reverse engineering is no longer the specialty of virus authors the way it used to be; a totally mainstream application of reverse engineering, practiced by most major security companies, is reverse engineering patches to find the underlying security flaws they fix so they can be weaponized.
It is easy to hide flaws in any code. Assembly doesn't make it much easier.
In particular, reverse engineering is no longer the specialty of virus authors the way it used to be; a totally mainstream application of reverse engineering, practiced by most major security companies, is reverse engineering patches to find the underlying security flaws they fix so they can be weaponized.
It is easy to hide flaws in any code. Assembly doesn't make it much easier.