Notice Heat and battery too
Does the mining use GPU? I would think most of the computers with an SMB vulnerability would not have GPUs worth exploiting. Because mining doesn't use much memory, if it is run on low priority on the CPU, you wont notice a slowdown. If you mine on the GPU, there will be noticeable latency.
If the mining was limited to running on CPU while plugged in, the only thing most users could notice would be extra heat and fan revving. Eventually the victim might notice a higher electric bill