Qubes OS Is Complicated. KUHBS Makes It Easy!

The isolation Qubes OS provides using virtual machines massively increases the complexity and monetary cost (buying exploits on the black market) required for an attack to compromise your whole system remotely. However, governments and other well-funded actors can purchase sophisticated commercial surveillance software and access to zero-day exploits from private vendors. State actors or highly motivated criminals can also break into your apartment or office.

Criminals and state actors use AI to find zero-day vulnerabilities in applications you use. Zero-day vulnerabilities can also be bought on the black market. Using a zero-day exploit on any application you use, for example a browser, will give the attacker complete control of that browser and possibly the VM it runs in. Qubes and KUHBS cannot prevent this, but massively minimize the risk of one exploited application infecting other applications. Qubes OS uses Xen for virtual machines , which isolate applications from one another. Xen is also used by very large cloud computing companies, and hence finding a zero-day exploit for Xen is highly complicated, and buying one is very, very expensive.

If an application is exploited and the malware is persistently installed in the files the application permanently saves (like your downloaded emails), then this malware will persist even if you set up your laptop again from scratch and restore backups. KUHBS only backs up exactly the files required for each individual application. All of the operating system files of the VM the application is running in are not backed up, but are instead set up again using the KUHB code whenever you remove and install an application. Qubes OS also provides mechanisms to limit the persistence of exploits across VM reboots. However, if malware infects the files that are persistent in Qubes OS and backed up by KUHBS, Qubes OS and KUHBS cannot protect you from the persistence of malware.

Firmware is code that is unrelated to the operating system you install on your computer, for example the BIOS of your computer. If this is infected, the attacker has total control over your computer regardless of which operating system you install. Qubes OS and KUHBS cannot detect or remove malware from BIOS, UEFI, or other device firmware. In order for malicious firmware to be remotely installed on your computer, access to Qubes OS’s most secure VM (dom0) is required. If an attacker has physical access to your computer, the attacker can just install firmware on your device (a BIOS password can help).

The disk encryption provided by the default Qubes OS installation prevents an attacker from gaining access to the application files saved on your computer (for example your photos). They can, however, modify the files in the /boot partition of Qubes OS, which would allow them to later gain access to your applications’ files and the whole operating system (Qubes OS). As stated above in “Compromised Computer Firmware”, physical access also allows an attacker to modify the firmware of your computer. Physical access to your computer, especially while it is unlocked, should always be synonymous with a complete breach of security.

The isolation of applications provided by Qubes OS has nothing to do with the passwords you use for your online accounts. If your account username and passwords are compromised, for example through a successful phishing attack (a well-crafted email that asks you to log in to your email account to “fix something”, with a link to a website that almost looks like gmail.com), neither Qubes OS nor KUHBS can protect you from that.