This posting from the folks at F-Secure compares the structure of the first PC virus, Boot/Brain.A (which recently celebrated its 20th birthday) with that of the more recent W32/Bagle.AG. Coincidentally, multi-drug resistant tuberculosis is on the rise. Having just reviewed Nancy Forbes' Imitation of Life: How Biology is Inspiring Computing, I have to wonder: does the existence of anti-virus programs produce tougher computer viruses in the same way that more powerful drugs drive the evolution of real ones?