&gt; The PNG decoder has no access to the file system, network interfaces, user interfaces, or really anything but stdin and stdout and some memory.<p>So you&#x27;ve rediscovered what UNIX has allowed us to do for decades now.<p>Things like process isolation, memory isolation, file isolation, and hardware isolation aren&#x27;t new. UNIX systems offered mature implementations of them in the 1980s, if not before then.<p>Best of all, this functionality was offered without needing to resort to resource-intensive virtual machines or anything of that sort.<p>Those who want the level of isolation you propose have been able to get it for a long time now. They just tend not to, because it&#x27;s inconvenient and impractical for real world systems.