资料来源 : Free On-Line Dictionary of Computing

firewall code
     
        1. The code you put in a system (say, a telephone switch) to
        make sure that the users can't do any damage. Since users
        always want to be able to do everything but never want to
        suffer for any mistakes, the construction of a firewall is a
        question not only of defensive coding but also of interface
        presentation, so that users don't even get curious about those
        corners of a system where they can burn themselves.
     
        2. Any sanity check inserted to catch a {can't happen} error.
        Wise programmers often change code to fix a bug twice: once to
        fix the bug, and once to insert a firewall which would have
        arrested the bug before it did quite as much damage.
     
        [{Jargon File}]