Coming back to the topic of computer security, the TCP Wrapper is an example of such a safety net. I wrote it when my systems were under attack by someone who appeared to walk through walls.
Wietse VenemaHowever, writing software without defects is not sufficient. In my experience, it is at least as difficult to write software that is safe - that is, software that behaves reasonably under adverse conditions.
Wietse VenemaPostfix keeps running even if one Postfix process dies; Windows requires that someone restarts the service.
Wietse Venema