Today, PCs (laptops, desktops, etc.) generally work under what I'll call the "open PC" security model. Users have full, system administrator/developer-level access to their own machine. Users can install arbitrary software of their choice onto their PC. That software can do anything, or at least anything that the user can do. Software applications are not sandboxed; they can freely access all of the user's data and interact or tamper with all other applications (*). Essentially, every user is God on their own machine, and can grant that God status to any software application they choose to install.
You could view malware as one consequence of the "open PC" security model. If a user has the ability to install software of their choice, and if that software gets full access to their PC, then all an attacker needs to do is persuade the user to install a malicious piece of software, and the user is toast. Similarly, if applications aren't sandboxed, then all an attacker needs to do is compromise one of the user's applications, and then the user is toast (the attacker gains access to all of the user's data and can compromise all of the user's applications).
Currently, the "open PC" security model is deeply baked into the way that PCs work, and the way that PC operating systems work.
What other alternatives to the "open PC" model are there? If the industry wanted to move away from the "open PC" model over the next 5-10 years, what are some possible alternative paradigms that might be worth considering? What are their advantages and disadvantages?
For example, one competing paradigm is the "app" security model. In the "app" security model, users generally do not have full syadmin/developer-level access to their own machine (unless they take some special step, which most users don't take). Users can install apps, but for most users, the selection of apps is limited to some list that is curated in at least some minimal sense (there may be ways to sideload apps from other sources, but most users mostly don't do that). Before installing an app, there's some way to get a feeling for how safe or risky that choice is (e.g., through perusing reviews, the permissions the app requests, or other information). Apps are sandboxed. Each app is prevented from interfering with other apps; one app cannot access all of the user's data or interfere with other apps.
The app model is arguably is more resilient to malware: it makes it harder for an attacker to persuade users to install malicious software, and it limits the damage that a malicious or compromised app can do.
So, we could think of the "app" security model as one alternative to the "open PC" security model. Much of the mobile world has moved to an "app" security model, and we've even started to see some movement in this direction in the desktop space (e.g., Windows 8).
Another possible alternative might be the "appliance" model, where your PC is no longer a general-purpose computer and users no longer have full God power over their PC. Instead, system administration is outsourced to someone else (possibly your employer's sysadmin, or some other third-party company that does system administration). Some basic software applications might come pre-installed (e.g., a web browser, some office/productivity software), and you might not be able to install anything else, or you might be limited in what software applications you can install (e.g., you can only install applications that are on some whitelist of permitted applications). I'm calling this the "appliance" model, but other reasonable names might be the "whitelisting" or "outsourced system administration" model. This model might not be right for everyone, but you could imagine it might be suitable for some fraction of users.
Are there other, radically different security models that are worth considering? If we could completely change the security paradigm underlying computers and operating systems and computer architecture (starting over from scratch, if need be), are there other paradigms/security models that might enable significant benefits to security?
(*) Footnote: OK, I know I'm simplifying my description of the "open PC" model a little bit. I realize that modern desktop operating systems do draw some distinction between the user account and Administrator/root. However, in some sense, this is a detail. For instance, the user/root separation does not provide any isolation between applications. Most of the software we run runs at the user level, so in desktop OS's, any user application can still interfere with any other user application.