DARPA Looking to Reinvent Network Security, With Inspiration from Adaptive Biological Systems

"..modeled on the human immune system"

There is a huge amount we still don't know about the immune system. The layers of interacting checks and balances in that system are... extremely complicated. They should really say it is based on the 'concept' of an immune system, because I don't believe for a second they would seriously attempt to replicate the human system.

...this is going to give computers just more viruses! So new software will include anti-virus and anti-bacteria!

We must remember that even the highly evolved immune systems of various forms of life cannot prevent the ultimate result. That which lives - dies.

The analogy holds at another level, as well. The vast majority of human life-saving effort (and associated insurance cost) is expended during the last few weeks of life. Any computer which mimics immune system operation will necessarily notify the system architects, with its death rattle, perhaps, of the causes of its demise. By this manner, evolution can occur. Without evolution, immunity will not sustain.