Digital Biology? Very interesting post from T Lurksalot on the overzealousness of those who would call the internet a "digital ecosystem". He identifies two major problems with the use of this term:

The first obvious difference between digital and biological life is what I call the "You can't hold me down" principle. No matter how hard you try to destroy biological life-forms it is very difficult to succeed on a species wide basis. Despite tens, hundreds, or thousands of years of sustained human effort we have made essentially no progress at destroying the life-forms that create malaria, influenza, anthrax, AIDS, or nearly any other communicable disease (how ironic, then, that we seem perfectly capable of inadvertently causing extinctions). Antibiotics kill the weak, acting as an evolutionary sieve constantly straining the bio-space in search of hardier organisms. Contrast this with our digital environment. Pathogens here show none of the hardiness of their biological analogs--stopping Code Red II or Nimda is a largely mechanical exercise with today's antiviral tools. Download the new virus signatures and continue on your merry way. How different this is from treating anthrax, where doctors must concern themselves with side effects, preexisting conditions, allergies, and innumerable other complicating factors--just on the patient side of the equation. This doesn't take into account the never ending forward march of the Darwinian parade; every step we take against any pathogen introduces a powerful new evolutionary filter that quickly strains the bacterial gene pool for the necessary counter tools. Clearly, digital "life" is nowhere close to this level of complexity--introducing a fix for Nimda does not cause the virus to spontaneously mutate to avoid the fix. The other major difference between digital and biological systems appears at the level of entire ecosystems. Put simply, biological networks exhibit a far greater degree of interdependence among components and this tighter web leads to the formation of longer feedback loops (a useful proxy for overall system complexity as the presence of longer loops provides the mechanism by which extremely localized perturbations can cause cascading global changes).

One important point here is that the fidelity of digital replication is too high. The tradeoff between genetic adaptability and information integrity is a delicate one, and the swing towards fidelity is too strong to permit evolution in our computer networks. Some programs (like Code Red) do have self-modifying code and are among the most successful viruses, but most other do not. But another important point is that any candidate "digital organism" must evade the claws of the predator that rules the ecosystem: Man . Since mankind can kill most viruses/worms at will (as T Lurksalot notes) most viruses do not have an ecological niche. So what kind of program could carve out an ecological niche? What might work would be a program that threatened to delete important files or cause firmware damage if antivirus software was installed, causing little or no damage otherwise. Unlike current viruses which cause all the damage they can and thereby provide incentive for the host to kill them no matter what the cost, this hypothetical virus would present a reason to keep the infection around. In other words, the problem with current viruses is that they reduce their ability to propagate by unduly aggravating the host. This hypothetical virus would focus its energies on replication rather than destruction. If such a program also included replicating self-modifying code with a built in "error" rate at the right level of granularity (code segment? bit stream?) and provided for "horizontal gene transfer" (picking up pieces of code from other programs on the machine), I bet we'd see some very interesting things start to happen. For one thing, random deletions/insertions of code at the right level of granularity would likely result in unambiguously virulent infections that didn't wait for an antivirus installation before causing firmware damage. If our networks eventually became central enough to day-to-day life that we couldn't live without them, then it wouldn't be feasible to incur the massive systemic cost of shutting down network segments to kill the infection. For example, humans might eventually require persistent connections to wireless networks to control our cybernetic implants, just as we require food and water. This is probably not as far off as one might think - look how rapidly we became dependent on electric power. It would be wily indeed for a virus to infect the networks governing our power system, and the damage wrought by such an infection would be incalculably larger than even the worst commercial internet virus. Imagine the consequences if electric power generation in the US was curtailed or eliminated for a month.... I've often thought that an enterprising and unscrupulous CS grad student or terrorist could become infamous by doing the (relatively trivial) programming involved in creating a power system virus. Good thing that there aren't too many fellows who have both the will and the way....