in the biological world, multicellular computing has yet to
evolve a taboo against code transfer. Some especially sensitive
application areas such as government, military and financial IT
do best to prohibit code transfer. Their best is not good
enough. Recent nation-state attacks include Chinese attacks
against the US Department of Defense, Stuxnet a joint US/Israeli
exploit against Iranian nuclear sites, and Flame a very large
and multi-function US malware package that exploits flaws in
Windows Update. Banks and other financial institutions are
hacked far more often than the public realizes. Commercial
databases containing credit card and other private information
of consumers continue to be compromised all too often. And the
above cases occur despite professional management of the
computers involved. Despite the increasing seriousness of such
threats, many programmers find it difficult even to imagine a
world in which it is technically impossible to alter code in a
computer. Moreover, the PC revolution was