Multiple Whonix-Workstation ™
Whonix ™ is a secure operating system comprised of two virtual machines which are isolated both from each other and the host. This configuration averts many threats posed by malware, misbehaving applications and user error. While Whonix ™ protects against many real world threats,  it is still possible for skilled adversaries to compromise Whonix-Workstation ™ (Qubes-Whonix ™:
If a single Whonix-Workstation ™ is used for all anonymous activities and is exploited, the attacker gains access to available data and can monitor all online activity. To minimize the impact of a compromise, it is recommended to utilize multiple Whonix-Workstation ™ to compartmentalize different identities and/or additional software. Depending on individual preferences and requirements, a second, third ... nth Whonix-Workstation ™ VM can be created.
Multiple Whonix-Workstation ™ Rationale
Different torifed clients can be used in a completely isolated manner with Multiple Whonix-Workstation ™. By compartmentalizing each different identity or client, an attacker can only read the data in the compromised VM. For example, if Tor Browser in VM-1 was compromised it could not read a user's IRC identity in VM-2. 
One disadvantage of this configuration is that if the host Internet connection goes offline or Tor on Whonix-Gateway ™ (
sys-whonix) suddenly fails, then all Whonix-Workstation ™ will go offline simultaneously. If multiple Tor clients were running and abruptly stop in unison, a network observer could link these activities to the same person. For instance, a strong correlation is formed if two Tor users in one IRC channel go offline at exactly the same time.
Qubes-Whonix ™ vs Non-Qubes-Whonix ™
Qubes-Whonix ™ is the recommended choice for multiple Whonix-Workstation ™ because it is specifically designed for compartmentalization (a.k.a. sandboxing) of multiple running VMs. This provides significant speed and security advantages relative to the traditional Type 2 hypervisor model, where two (or more) Whonix ™ VMs are run inside programs like VirtualBox on top of the host OS. For further information, see: Type 1 vs Type 2 Hypervisors and Why use Qubes over other Virtualizers?
Qubes-Whonix ™ also has a TemplateBased filesystem which saves time and improves usability compared to Non-Qubes-Whonix ™:
- Centralized Updates: App Qubes [archive] are based on the corresponding Template's root filesystem. After updating the Template, those same updates will be reflected in the root filesystem of every App Qube [archive]. Non-Qubes-Whonix ™ users must spend more time in updating each VM individually.
- Minimal Disk Usage: App Qubes require far less disk space than traditional VMs since the App Qube's root filesystem is based on the corresponding template. The App Qube only requires enough disk space to hold user files in the
- VM Management: Cloning VMs is a simple two-step process which can be done in Qube Manager. Non-Qubes-Whonix ™ requires a multi-step process to clone and configure each VM.
It is safest to only use one Whonix-Workstation ™ at a time and for a single activity. New risks are introduced by running multiple Whonix-Workstation ™ at the same time. For instance, if a single Whonix-Workstation ™ was compromised, it could potentially perform various side channel attacks to learn about running processes in other VMs, and not all of these can be defeated. Depending on user activities, a skilled adversary might be able to correlate multiple Whonix-Workstation ™ to the same pseudonym. Therefore, ideally, shut down all but one Whonix-Workstation ™ before using any other Whonix-Workstation ™.
Cross-VM Attack Vectors
Table: Cross-VM Attack Vectors
|Attacks via the shared bridge||
Multiple workstation VMs are all connected to the gateway using the same virtual bridge; they share an IP subnet. A variety of attacks permit devices sharing a bridge to view or steal one another's traffic, or to impersonate one another at the IP layer. The exact attacks available depend on the specific bridge implementation, but some are always available. At a minimum, VMs sharing a bridge can always trivially detect one another, and determine one another's local IP addresses on the bridge, simply by watching broadcast traffic like ARP and IPv6 neighbor discovery.
The snooping and impersonation vulnerabilities are particularly dangerous because the communication between the Tor process running on the gateway and the client programs running on the workstation is neither encrypted nor cryptographically authenticated. Connections are made either using the (cleartext) SOCKS5 protocol or using Tor's transparent connection proxying feature. Even if the actual application data are encrypted, DNS lookups and circuit creation data are always sent in the clear. A workstation VM that intercepts another workstation's bridge traffic is in a position to know the destinations of all outgoing connections over Tor from that other workstation, as well as the timing and volume of traffic sent over each such connection. It may also be possible to intercept Tor control traffic generated by the "new identity" button. If the user sends cleartext data at the actual application layer, then hostile VMs are in a position to steal those data as well.
In effect, none of the workstation VMs receives Tor's core protections with respect to the other workstation VMs. Although many things in each workstation may be protected against the other workstations, for Tor purposes all of the VMs effectively share the same compartment.
This could be mitigated by providing each workstation VM with a separate virtual bridge and a separate virtual interface on the gateway VM. The gateway configuration should also be reviewed to make sure that the gateway isn't routing unnecessary traffic between the workstations at the IP layer.
For a potential remedy see Connections between Whonix-Gateway ™ and Whonix-Workstation ™.
|Distributed Denial of Service (DDOS) Attack||
An adversary that managed to compromised a VM with malware could stress any system such as CPU, GPU, HDD, RAM, network connection and other Whonix-Workstation ™. If a Distributed Denial of Service (DDOS) Attack [archive] is launched from an infected Whonix ™ VM, then:
|Local VM Fingerprinting||See VM Fingerprinting.|
|Exploits against other Whonix-Gateway ™ ||
Following infection, an adversary could try to exploit the Whonix-Gateway ™.
|Exploits against other Whonix-Workstation ™||Following infection, an adversary could try to exploit other Whonix-Workstation ™:
|Identity Correlation through Circuit Sharing||
When different applications use the same Tor circuit and exit relay, these activities can be linked to the same pseudonym (see Stream Isolation for further details):
Multiple Whonix-Workstation ™ are supposed to have different internal IPs configured. Once a VM is compromised by malware it could attempt to impersonate another VM by taking its internal IP.
How-to: Use more than One Whonix-Workstation ™ - Easy
Using multiple Whonix-Workstation ™ is simple in Qubes-Whonix ™.
If you are interested in this configuration, please press on Expand on the right.
How-to: Use more than One Whonix-Workstation ™ - More Security
- Qubes-Whonix ™: This step can be skipped. 
- Non-Qubes-Whonix ™: See: Connections between Whonix-Gateway ™ and Whonix-Workstation ™.
Multiple Whonix-Gateway ™
Moved to Multiple Whonix-Gateway ™.
- See: Protection Against Real World Attacks.
- Without using an additional exploit to successfully break out of the infected VM, which is a difficult task.
- By default, App Qubes which are behind the same ProxyVM (or NetVM) are prevented from connecting to each other in Qubes.
- To minimize the threat of exploits it is recommended to apply relevant instructions found in the System Hardening Checklist.
- Since IsolateClientAddr [archive] is the Tor default.
- Sparing users from needing to change this setting requires upstream Qubes feature request way to find out name of gateway from witin VM - qubesdb-read /qubes-gateway-name [archive] or qrexec feature request: send this over qrexec to the NetVM I am connected to / sys-whonix hardcoded / sys-whonix unexpected autostart [archive] to get implemented.
- https://forums.whonix.org/t/sys-whonix-starting-spontainously-after-update/8123 [archive]