Not long ago appeared an idea about virus, consisting of only NOPs. Let we have such typical program, that its code (in different places, but consecutively) contains the same instructions, blocks of instructions or their functional variants, those can be used in some virus. Then, it will be enough to fill all other part of that program's code with NOPs, so all remaining instructions will become the virus itself. Thus, from viewpoint of performed midifications, virus will consist of only NOPs. This can be not only the simple program, but program with all its DLLs; moreover, we can insert not only NOPs, but lots of other garbage. In other words, standard infection by means of adding new instructions here changed into inverse operation, that removes unnecessary instructions. Of course, there will be troubls with constants; but if you're interested in, you will invent something.