|short stream isolation summary||all information below|
- 1 Introduction
- 2 List
- 3 Details
- 4 Footnotes
- 5 How to mitigate identity correlation
- 6 Deactivate Stream Isolation
- 7 Development
- 8 Sources
- 9 References
If you install custom applications and do not explicitly take precaution against identity correlation through Tor circuit sharing, you risk that different activities, let's say Web (Chromium or similar) or IRC (mIRC or similar) go through the same Tor circuit and exit relay. Even though you would still be anonymous, i.e. the Tor exit relay would still not know your real IP/location, they can easily correlate those activities issued by different applications to the same pseudonym.
The following graphic illustrates the difference of using Tor SocksPort's compared to using Tor's TransPort. Using dedicated Tor SocksPort's per application results in taking different routes through the Tor network per application. Not necessarily all nodes (first, second, third) get replaced by Tor. Sometimes just the first, sometimes just the second, sometimes just the third, and sometimes multiple nodes change.
Whonix implements protection against identity correlation through Tor circuit sharing for preinstalled applications, however, for better privacy, you are still advised to understand a bit of the technical background. Since Tor version 0.2.3, different Socks,- Dns-, or TransPorts go through different Tor circuits, therefore preventing identity correlation. Whonix configures most applications that come preinstalled with Whonix to use different SocksPort, thus no identity correlation is at risk. Whonix uses either socks proxy settings to direct various applications to different SocksPorts or uwt (more information below).
Any other traffic (i.e. custom installed applications, misc applications, such as nslookup, go through Tor's Dns-, and/or TransPort (can be optionally disabled, see below).
Applications in Whonix, that are either prepared or fully pre-configured to prevent identity correlation through Tor circuit sharing:
|application||pre-installed||pre-configured||stream isolation by method||port||comments|
|Tor Browser||yes||yes||socks proxy settings||9150 ||-|
|HexChat (and see Chat#General Safety Advice)||yes||yes||socks proxy settings||9101||-|
|Mozilla Thunderbird with TorBirdy||no||yes||socks proxy settings||-||-|
|Tor Messenger||no||yes||socks proxy settings||9152||-|
|Instant Messenger (see Chat)||no||no (TODO)||socks proxy settings||port prepared, IP 10.152.152.10, port 9103||-|
|sdwdate||yes||yes||socks proxy settings||-||-|
|whonixcheck||yes||yes||socks proxy settings||9110||-|
|BitCoin (see Money)||no||no||socks proxy settings||port prepared, IP 10.152.152.10, port 9111||-|
|privoxy||no||no||socks proxy settings||port prepared, IP 10.152.152.10, port 9112||-|
|polipo||no||no||socks proxy settings||port prepared, IP 10.152.152.10, port 9113||-|
|Tor Browser Downloader by Whonix||yes||yes||socks proxy settings||-||-|
|Chat#Ricochet IM||no||yes||socks proxy settings||-||connects only to onion services|
|Mixmaster||yes||yes||settings ||-||connects only to onion services|
|KDE application wide proxy settings||no||yes||socks proxy settings||9122 no KDE applications with network activity pre-installed||-|
By uwt wrapper
|application||pre-installed||pre-configured||stream isolation by method||port||comments|
|apt-get (see Update)||yes||yes||uwt wrapper||-||-|
|scurl||yes||yes||Uses curl, therefore same as curl.||-||-|
|mixmaster-update (see Mixmaster)||yes||yes||uwt wrapper||-||-|
|application||pre-installed||pre-configured||stream isolation by method||port||instructions|
|GNOME application wide proxy settings||no||no||none||no GNOME applications with network activity pre-installed||-|
The required socks proxy settings are setup by various Whonix configuration packages or uwt wrappers, which are set up on Whonix-Gateway and on Whonix-Workstation. uwt is a wrapper around torsocks, which is also already installed to .
- Example, each time you run a uwt wrapped application, i.e. simply type apt-get in console, the uwt wrapper will run. It adds uwt before apt-get. For curiosity check . Essentially, the uwt wrapper then runs . That is also the case for all other uwt wrapped applications.
- If you ever want or must run a uwt wrapped application without uwt, do not run for example #Deactivate_uwt_Stream_Isolation_Wrapper. in console, do run . Use cases could be if you want to connect to localhost. If you know what you are doing, you should also be able to deactivate any uwt wrappers you dislike, see
- When running /usr/bin/apt-get.anondist-orig it directly goes through Tor's DnsPort and through Tor's TransPort and not through its own SocksPort.
- uwt looks if the command contains the words localhost or 127.0.0.1, if that is the case, uwt will not be used. The command will be run without uwt. Thus, if a localhost connection is falsely detected it will leak, but only through Tor's DnsPort and through Tor's TransPort, which should be acceptable.
Isolate by destination address: Let's assume SSH goes over port 22 and you want to connect to different SSH servers and do not want an observer to be able to correlate that activity to the same pseudonym. If the SSH servers run on different IP's isolate by destination address might help.
Isolate by destination port: This doesn't seem to be useful for anything in Whonix, applications using different protocols (and therefore different ports) are already isolated through using different SOCKSPorts.
Isolate by destination port doesn't really achieve anything for web browsing: tor-talk Tor's stream isolation features defaults.
For more information about stream isolation refer to the Tor manual.
Different tabs and websites in Tor Browser are isolated by since Tor Browser version 4.5-alpha-1. 
- Whonix-Workstation 127.0.0.1:9150 gets redirected to 10.152.152.10:9150 by rinetd. See on Whonix-Workstation file /etc/rinetd and package anon-ws-disable-stacked-tor. Changing proxy settings in Tor Browser has proven to be unreliable. At some point Tor Button may change its internals and therefore break something again. Keeping the default settings and not requiring any changes in Tor Browser seems like the best way to support compatibility in long run and also is simplest in case breaks and manually updating Tor Browser is required again in future.
- (see also Dev/Mixmaster)
How to mitigate identity correlation
If you install custom software on Whonix-Workstation, that uses the internet, and want to prevent identity correlation through Tor circuit sharing (which you should do), you have to manually configure them. This is not a Whonix specific problem.  Read also Software installation on Whonix-Workstation.
A #list of applications which come pre-installed with Whonix are pre-configured to prevent identity correlation through circuit sharing.
Traffic going through TransPort by default is whonixcheck when testing the TransPort. If that is of concern to you, it can be disabled in whonixcheck, see Advanced Security Guide#Prevent polluting TransPort.
All custom installed application's TCP traffic is routed through Tor's TransPort and all their DNS requests through Tor's DnsPort. This means different activities or "identities" in different applications (say browser, IRC, email) end up being routed through the same circuit, thus identity correlation is at risk. 
To protect against this, you have to set up per-application SOCKS ports in Whonix-Gateway.
On Whonix-Gateway in /usr/share/tor/tor-service-defaults-torrc are already a lot custom socks ports prepared for custom installed applications:
- Without IsolateDestAddr and without IsolateDestPort: SocksPort 10.152.152.10:9153 to 9159
- With IsolateDestAddr, but without IsolateDestPort: SocksPort 10.152.152.10:9160 to 9169
- Without IsolateDestAddr, but with IsolateDestPort: SocksPort: 10.152.152.10:9170 to 9179
- With IsolateDestAddr and with IsolateDestPort: SocksPort: 10.152.152.10:9180 to 9189
- If they those are not enough, you can add your own ones.
What are IsolateDestAddr and IsolateDestPort? You can learn about them in the Tor manual. See also tor-talk mailing list: Tor's stream isolation features defaults. Usually, unless you know better, you are better off not using IsolateDestAddr or IsolateDestPort.
You can point your applications, where you want to prevent identity correlation though circuit sharing, to those SocksPorts. Each custom installed application has to be torified, for directions how to do that use the Torify HOWTO.
Additional comments regarding the Torify HOWTO:
- Warnings about protocol related warnings you must honor. You are still better off with Whonix, as it offers best possible Protocol-Leak-Protection and Fingerprinting-Protection.
- Whonix's setup provides protection against IP leaks through protocol leaks.
- If you do not correctly torify either no connections will be possible or traffic will either continue going through Tor's TransPort (unless you disable that, as explained below).
- If you redirect more than one application to the same SocksPort, identity correlation is at risk.
- DNS related warnings still apply, though to a lesser extent - an attack could only make correlations but still couldn't figure out your IP. You can prevent that, be out commenting (# in front) DnsPort in /etc/tor/torrc on the Whonix-Gateway and by removing the DNS redirection firewall rule from /usr/bin/whonix_firewall.
- Do not use a local DNS resolver, as all DNS requests would be executed by the same circuit.
- Other leaks, such as applications not honoring the proxy settings / wrapper, ICMP or UDP leaks do not apply to Whonix.
- The SafeSocks setting is for rejecting unsafe variants of socks that might cause DNS leaks. The Whonix design model mitigates DNS leaks by redirecting all requests to Tor's DnsPort. Enabling this setting would give marginal benefit in this situation but would complicate debugging.
For best protection against identity correlation:
Read the advice above and on Whonix-Gateway:
Deactivate KDE / GNOME - application wide proxy settings...
- Because those proxy settings are not application specific, but rather force all KDE / GNOME applications through the same SocksPort (no KDE / GNOME applications which use the internet preinstalled by default), deactivating those KDE / GNOME - wide proxy settings gives better control about stream isolation.
To deactivate TransPort and DnsPort...
Modify Whonix User Firewall Settings
3) Reload Whonix-Gateway Firewall.
This will disable transparent proxying. All applications not configured to use a SocksPort by socks proxy settings or forced to use a SocksPort by a socksifier will not be able to establish connections. This is the only way to ensure, that different SocksPorts are used and that also DNS is remotely resolved through that SocksPort.
Deactivate Stream Isolation
How to disable stream isolation. Most easy and common methods only. For more options, see below.
Deactivate uwt Stream Isolation Wrapper
OPTIONAL. Usually not required. Only for special setups and people who know what they are doing.
Append .anondist-orig to the command you want to run. For example, instead of using.
UWT_DEV_PASSTHROUGH=1 curl 188.8.131.52
Environment Variable Method
Use the UWT_DEV_PASSTHROUGH environment variable. 
Example. Set the UWT_DEV_PASSTHROUGH environment variable. This will disable using torsocks for all following invocations.
When running as user and using sudo, do not forget sudo's -E parameter which stands for preserve environment.
sudo -E apt-get update
You can enable/disable all uwt stream isolation wrappers globally or enable/disable specific stream isolation wrappers, see uwtconfiguration file.
deactivate all uwt wrappers permanently
Deactivate Misc Proxy Settings
Tor Browser Remove Proxy Settings
If you would like to remove proxy settings from Tor Browser, see below.
1. Applications which internally use curl.
sudo update-flashplugin-nonfree --install --verbose
2. Applications which is uwt wrapped itself and internally uses ssh.
git push origin master
Debugging / List of all uwt wrappers
sudo dpkg-divert --list
ls -la /usr/bin/ssh
Deactivating an uwt wrapper
sudo unlink /usr/bin/ssh
sudo dpkg-divert --rename --remove /usr/bin/ssh
Check if Transparent DNS is disabled
nslookup check.torproject.org ; echo $?
;; connection timed out; no servers could be reached 1
If it shows something else, such as a resolved IP, the Transparent DNS is enabled.
Check if Transparent TCP is disabled
UWT_DEV_PASSTHROUGH=1 curl 184.108.40.206 ; echo $?
curl: (7) couldn't connect to host 7
If it shows something else, such as the html source code, then Transparent TCP is enabled.
Check if Transparent Proxying is disabled
UWT_DEV_PASSTHROUGH=1 curl https://check.torproject.org/ ; echo $?
curl: (6) Couldn't resolve host 'check.torproject.org' 6
If it shows something else, such as the html source code, then Transparent Proxying is enabled.
Whonix 14 and above
To test this, run multiple times the following command.
scurl https://check.torproject.org | grep IP
Check if an Application is properly using Stream Isolation
- Same as
leak testingas if Whonix is not involved.
- Also... A weaker test... The
transparent proxying disablementtest.
Disable transparent proxying of DNS and TCP as per #Better Protection.
Check that worked as per:
That is because it doesn't work without transparent proxying (system default networking), meaning application unable to use network normally, then there is a certain socks leak, meaning certainly some traffic which requires system default networking. In case of:
- clearnet operating systems: a clearnet leak
- Whonix: a stream isolation violation
This is only weak test since an application could very likely try socks first and if socks fails, fall back to system default networking. Therefore, normal
leak testing is required.
- Internet research if application was specifically designed for use with Tor.
- Internet research if application was specifically audited for clearnet leaks.
- Discussion with software maintainer about this if these haven't already happened.
- corridor - Tor traffic whitelisting gateway
- Separate streams across circuits by connection metadata
- tor-talk Operating system updates / software installation behind Tor Transparent Proxy
- tor-talk Awareness for identity correlation through circuit sharing is almost zero.
- tor-talk Tor's stream isolation features defaults Question
- tor-talk Tor's stream isolation features defaults Answer
- Tails-dev separate Tor streams
- Tails separate Tor streams
- Tails-dev Please review Tails stream isolation plans
- Tails Design: Tor stream isolation
Stream Isolation Graphic has been contributed by: Cuan Knaggs – graphic and web design revlover print media – web design – web development – cms – e-commerce
- If you used to use only one SocksPort with the common torification methods, the same thing happened.
- What about UDP? See Tor#UDP.
Although not strictly required, you could alternatively/additionally add to /etc/tor/torrc.
For Whonix 14 and later releases, all unique Tor configurations should be stored in /usr/local/etc/torrc.d/50_user.conf. Users should not edit /etc/tor/torrc directly.
TransPort 0 DnsPort 0
And then Reload Tor.
- Multiple Whonix-Workstations using different internal IP's are automatically separated by Tor (IsolateClientAddr is Tor's default).
TB_NO_TOR_CON_CHECK=1needs to be set because there is no filtered Tor ControlPort access when Whonix tunnel firewall is enabled, which would break tb-updater's Tor connectivity check.
By tb-updater default, if unset, variable
CURL_PROXYwill be dynamically set to a Tor SocksPort on Whonix-Gateway. For example to
By using a curl parameter we are using anyhow, i.e.
CURL_PROXY="--fail"we can in effect disable the environment variable even if it's technically still set. This will result in downloading by using the system's default networking.
- This term was coined in context of a Tor Transparent Proxy. It acts as a simple gateway that routes all connections through Tor, but does not provide Stream Isolation.
- Unless this environment variable is manually unset before starting Tor Browser.
- The regular Tor Browser Bundle from The Tor Project (without Whonix) allows networking settings to changed inside Tor via the
Open Network Settingsmenu option. It has the same effect as editing Tor's config file torrc. In Whonix, the environment variable
export TOR_NO_DISPLAY_NETWORK_SETTINGS=1has been set to disable the
Open Network Settings...menu item. It is not useful and confusing to have in the Whonix-Workstation because:
https | (forcing) onion
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