I find this footnote fascinating. It seems implicitly to assume that within a computer used by just one person there are no conflicts of interest. The authors seem to assume that all damage to one program by another is accidental—as if the computer user had written all of the code in the computer. See this for a very real conflict within a single user system. The perspective that now seems strange is that it is manifestly clear what I want software to do and that I can expect software that I buy to do exactly that. In short the conflicts I now see are between producers of software for the computer rather than between users of the computer. For me, computer security is how I would enforce the policies within my computer so that the software systems that I have cobbled together continue to work as I add new software from yet new sources.