Patching an OS isn't new, but patching an OS to enable a virus? That might be. Linus Torvalds has recently patched the Linux kernel to fix a small bug that was revealed during the testing of a proof-of-concept cross platform virus. Fixing the bug enables the virus to work as it should. Though Torvalds doesn't seem to think that Virus.Linux.Bi is much of a virus, just a program that has an interesting way of writing to files for which it has permissions. For more details, the stories can be found here and here.