nShortest virus is 101 bytes
nThere are 10243 possible files of length 101 bytes.
nIf we have all 100 million PCs in world run full-time, making only
101-byte files at 1000/sec:
nProbability (hist univ) = 4 x 10-214
nIf every elementary particle in universe such a PC, then Probability = 6
x 10-100