Qubes is an open-source operating system designed to provide strong security for desktop computing using Security by Compartmentalization approach. Qubes is based on Xen, the X Window System, and Linux, and can run most Linux applications and utilize most of the Linux drivers. Qubes Release 1 was released in September 2012 andRelease 2 in September 2014. Qubes also supports Windows-based AppVMs beginning with Release 2 (currently in “Beta”). Qubes Release 3 is coming soon and will introduce Hypervisor Abstraction Layer (HAL), allowing easy porting to alternative virtualization systems.
A Simple Introduction to Qubes
This is a short, non-technical introduction to Qubes intended for a popular audience. (If you just want to quickly gain a basic understanding of what Qubes is all about, you’re in the right place!)
What is Qubes?
Qubes is a security-oriented operating system (OS). The OS is the software which runs all the other programs on a computer. Some examples of popular OSes are Microsoft Windows, Mac OS X, Android, and iOS. Qubes is free and open-source software (FOSS). This means that everyone is free to use, copy, and change the software in any way. It also means that the source code is openly available so others can contribute to and audit it.
Why is OS security important?
Most people use an operating system like Windows or OS X on their desktop and laptop computers. These OSes are popular because they tend to be easy to use and usually come pre-installed on the computers people buy. However, they present problems when it comes to security. For example, you might open an innocent-looking email attachment or website, not realizing that you’re actually allowing malware (malicious software) to run on your computer. Depending on what kind of malware it is, it might do anything from showing you unwanted advertisements to logging your keystrokes to taking over your entire computer. This could jeopardize all the information stored on or accessed by this computer, such as health records, confidential communications, or thoughts written in a private journal. Malware can also interfere with the activities you perform with your computer. For example, if you use your computer to conduct financial transactions, the malware might allow its creator to make fradulent transactions in your name.
Aren’t antivirus programs and firewalls enough?
Unfortunately, conventional security approaches like antivirus programs and (software and/or hardware) firewalls are no longer enough to keep out sophisticated attackers. For example, nowadays it’s common for malware creators to check to see if their malware is recognized by any popular antivirus programs. If it’s recognized, they scramble their code until it’s no longer recognizable by the antivirus programs, then send it out. The best antivirus programs will subsequently get updated once the antivirus programmers discover the new threat, but this usually occurs at least a few days after the new attacks start to appear in the wild. By then, it’s typically too late for those who have already been compromised. In addition, bugs are inevitably discovered in the common software we all use (such as our web browsers), and no antivirus program or firewall can prevent all of these bugs from being exploited.
How does Qubes provide security?
Qubes allows you to separate the various parts of your digital life into securely isolated virtual machines (VMs). A VM is basically a simulated computer with its own OS which runs as software on your physical computer. You can think of a VM as a computer within a computer. This allows you to have, for example, one VM for visiting untrusted websites and a different VM for doing online banking. This way, if your untrusted browsing VM get compromised by a malware-laden website, your online banking activities won’t be at risk. Similarly, if you’re concerned about risky email attachments, Qubes can make it so that every attachment gets opened in its own single-use, “disposable” VM.
In general, Qubes takes an approach called security by isolation, which in this context means keeping the things you do on your computer securely isolated in different VMs so that one VM getting compromised won’t affect the others. This allows you to do everything on a single physical computer without having to worry about one successful cyberattack taking down your entire digital life in one fell swoop.
How does Qubes compare to using a “live CD” OS?
Booting your computer from a live CD (or DVD) when you need to perform sensitive activities can certainly be more secure than simply using your main OS, but this method still preserves many of the risks of conventional OSes. For example, popular live OSes (such as Tails and other Linux distributions) are still monolithic in the sense that all software is still running in the same OS. This means, once again, that if your session is compromised, then all the data and activities performed within that same session are also potentially compromised.
How does Qubes compare to running VMs in a convential OS?
Not all virtual machine software is equal when it comes to security. You may have used or heard of VMs in relation to software like VirtualBox or VMware Workstation. These are known as “Type 2” or “hosted” hypervisors. (Thehypervisor is the software, firmare, or hardware that creates and runs virtual machines.) These programs are popular because they’re designed primarily to be easy to use and run under popular OSes like Windows (which is called thehost OS, since it “hosts” the VMs). However, the fact that Type 2 hypervisors run under the host OS means that they’re really only as secure as the host OS itself. If the host OS is ever compromised, then any VMs it hosts are also effectively compromised.
By contrast, Qubes uses a “Type 1” or “bare metal” hypervisor called Xen. Instead of running inside an OS, Type 1 hypervisors run directly on the “bare metal” of the hardware. This means that an attacker must be capable of subverting the hypervisor itself in order to compromise the entire system, which is vastly more difficult.
Qubes makes it so that multiple VMs running under a Type 1 hypervisor can be securely used as an integrated OS. For example, it puts all of your application windows on the same desktop with special colored borders indicating the trust levels of their respective VMs. It also allows for things like secure copy/paste operations between VMs, securely copying and transferring files between VMs, and secure networking between VMs and the Internet.
How does Qubes compare to using a separate physical machine?
Using a separate physical computer for sensitive activities can certainly be more secure than using one computer with a conventional OS for everything, but there are still risks to consider. Briefly, here are some of the main pros and cons of this approach relative to Qubes:
Pros:
- Physical separation doesn’t rely on a hypervisor. (It’s very unlikely that an attacker will break out of Qubes’ hypervisor, but if she were to manage to do so, she could potentially gain control over the entire system.)
- Physical seaparation can be a natural complement to physical security. (For example, you might find it natural to lock your secure laptop in a safe when you take your unsecure laptop out with you.)
Cons:
- Physical separation can be cumbersome and expensive, since we may have to obtain and set up a separate physical machine for each security level we need.
- There’s generally no secure way to transfer data between physically separate computers running conventional OSes. (Qubes has a secure inter-VM file transfer system to handle this.)
- Physically separate computers running conventional OSes are still independently vulnerable to most conventional attacks due to their monolithic nature.
- Malware which can bridge air gaps has existed for several years now and is becoming increasingly common.
Visit: https://www.qubes-os.org
Select Qubes OS Screenshots
Starting applications from different domains (AppVMs) is very easy.
In this example, the word processor runs in the “work” domain, which has been assigned the “green” label. It is fully isolated from other domains, such as the “untrusted” domain (assigned the “red” label – “Watch out!”, “Danger!”) used for random Web browsing, news reading, as well as from the “work-web” domain (assigned the “yellow” label), which is used for work-related Web browsing that is not security critical. Apps from different domains run in different AppVMs and have different X servers, filesystems, etc. Notice the different color frames (labels) and VM names in the titlebars. These are drawn by the trusted Window Manager running in Dom0, and apps running in domains cannot fake them:
Qubes Release 2 can also run Windows AppVMs in seamless mode, integrated onto the common Qubes trusted desktop, just like Linux AppVMs! The seamless GUI integration has been introduced in Qubes R2 Beta 3. This requires our dedicated Qubes Windows Support Tools to be installed in the Windows VMs first. The Qubes Windows Tools are proprietary but we distribute the binaries for free with current Qubes OS releases.
Windows AppVMs are fully integrated with the rest of the Qubes OS system, which includes things such as secure, policy governed, inter-VM file copy, clipboard, and generally whole our elastic qrexec infrastructure for secure inter-VM RPC! Starting with Qubes R2 Beta 3 we also support HVM-based templates allowing to instantly create many Windows AppVMs with shared “root filesystem” from the Template VM (but one should ensure their license allows for such instantiation of the OS in the template). Just like with Linux AppVMs!
Here we see Xfce4.10 Window Manager running in Dom0 (instead of KDE as on previous screens). Qubes supports customized Xfce4 in dom0 beginning with R2 Beta 2!
It is always clearly visible to which domain a given window belongs. Here it’s immediately clear that the passphrase-prompting window belongs to some domain with the “green” label. When we look at the titlebar, we see “[work]”, which is the name of the actual domain. Theoretically, the untrusted application (here, the “red” Firefox) beneath the prompt window could draw a similar looking window within its contents. In practice, this would be very hard, because it doesn’t know, e.g., the exact decoration style that is in use. However, if this is a concern, the user can simply try to move the more trusted window onto some empty space on the desktop such that no other window is present beneath it. Or, better yet, use the Expose-like effect (available via a hot-key). A malicious application from an untrusted domain cannot spoof the whole desktop because the trusted Window Manager will never let any domain “own” the whole screen. Its titlebar will always be visible.
Qubes is all about seamless integration from the user’s point of view. Here you can see how it virtualizes tray icons from other domains. Notice the network icon in a red frame. This icon is in fact managed by the Network Manager running in a separate NetVM. The notes icon (with the green frame around it) has been drawn by the note-taking app running in the work domain (which has the “green” label).
All the networking runs in a special, unprivileged NetVM. (Notice the red frame around the Network Manager dialog box on the screen above.) This means that in the event that your network card driver, Wi-Fi stack, or DHCP client is compromised, the integrity of the rest of the system will not be affected! This feature requires Intel VT-d or AMD IOMMU hardware (e.g., Core i5/i7 systems).
Qubes lets you update all the software in all the domains all at once, in a centralized way. This is possible thanks to Qubes’ unique TemplateVM technology. Note that the user is not required to shut down any AppVMs (domains) for the update process. This can be done later, at a convenient moment, and separately for each AppVM.
Qubes supports secure copy-and-paste operations between AppVMs. Only the user can initiate a copy or paste operation using a special key combination (Ctrl-Shift-C/V). Other AppVMs have no access to the clipboard buffer, so they cannot steal data from the clipboard. Only the user decides which AppVM should be given access to the clipboard. (This is done by selecting the destination AppVM’s window and pressing the Ctrl-Shift-V combination.)
Qubes also supports secure file copying between AppVMs.
Qubes’ unique Disposable VMs (DispVMs) allow the user to open any file in a disposable VM in a matter of seconds! A file can be edited in a disposable VM, and any changes are projected back onto the original file. Currently, there is no way to mark files to be automatically opened in a disposable VM (one needs to right-click on the file and choose the “Open in Disposable VM” option), but this is planned for the R2 Beta 3 release.
Qubes provides an advanced infrastructure for programming inter-VM services, such as a PDF converter for untrusted files (which is described in this article).
Qubes provides a dedicated firewall that itself runs in an isolated FirewallVM.
And some more screenshots:
The following screenshots, courtesy of Qubes user nalu, demonstrate some of the ways in which KDE can be customized to work with Qubes:
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