Uwe Hermann - HOWTO: Anonymous communication with Tor - some hints and some pitfalls [Update] - Comments

some misunderstanding

Anonymous — Mon, 01 Feb 2010 07:34:06 +0100

What he meant was that the first node in the circuit can actually see the data and the last node can see it also.... traffic is encrypted all the to the entry node, but entry node can see what's in it.... only relay can't see what's in it. it=packets

Bridges

Anonymous — Sun, 11 Oct 2009 03:57:36 +0200

Tor / Hotspot / Freegate are all blocked.

Can someone please either set up a bridge for me or mail me some Bridges info.

Hi there. What I want to do

Anonymous — Fri, 24 Jul 2009 15:10:49 +0200

Hi there.

What I want to do is pretty simple, but I need to know if what I am doing is completely anonymous.

Ok so im new to Tor and all this stuff.

What I want to do is essential send and receive e mails to my contacts completely anonymously, and untraceable.

So what ive understood so far. I use Tor to encrypt and mask my isp from my computer to the last node, the exit node, and then use Privoxy which will revent DNS leaks. This will make me completely anonymous?

So if I configure firefox with Tor and Proivoy and use a web e mail service then like hushmail? Will I be untraceable and secure?

or is there more I need to know?

Even hushmail aside.. could I use gmail and be equally protected?

torify ncftp

Keiner — Sat, 11 Jul 2009 10:25:37 +0200

Uwe,
Have you tried system-wide DNS' queries interception by Tor which i (not so well) described in comment to your post "Anonymous Google Earth over Tor" (comment "waits admin's moderation").
After all is done, "torify ncftp" should not leak DNS.

Re: Tor traffic

Keiner — Thu, 02 Jul 2009 20:01:24 +0200

Uwe, now i understand what you mean. Thank you for reply and explaining.

Tor traffic

Uwe Hermann — Thu, 02 Jul 2009 00:28:40 +0200

Hi, I think this is a misunderstanding or maybe I misworded my text. Yes, traffic does leave your PC in encrypted form already, so the ISP should not be able to sniff any unencrypted Tor traffic from you.

I guess what I was referring to back then as "at the beginning" was the local PC where your Tor daemon runs. If this PC is not fully under your (and only your) control, you might still compromise your anonymity. Say you use Tor on some Uni/company PC where someone other than you has a root login or similar. In that case the root user may well be able to sniff whatever you want to pass into the Tor network before it gets sent away, i.e., in its plain-text unencrypted form.

This is just a theoretical scenario right now, I don't know about any concrete rootkits or other ready-made software that does something like this, but the risk is definately there. Using manipulated shared libraries, manipulated Tor daemon software, rootkit software, or through other means — a local attacker with root permissions will certainly be able to see your Tor traffic before it gets encrypted and sent into the Tor network.

Of course, if someone other than you has root permissions on such a box, you also have many other problems... Anyway, I would definately not recommend using Tor on machines you don't fully control.

Uwe.

Does traffic really leaves client machine unencrypted?

Keiner — Wed, 01 Jul 2009 22:44:23 +0200

Uwe, good article, thanks
(for me i found interesting a note about reaching ftp resource thru proxified web browser and resulting loss of tor's protection).

What about correcting a following yours note:
"...Tor only anonymizes your traffic, but it can still be sniffed plain-text AT THE BEGINNING and at the end of the onion route!.." --uppercase by me.

What your statement means to me (and probably others): traffic leaves client machine unencrypted and can be intercepted (e.g. by ISP) at the way it travels to the first server in the route. Even if client machine is supposed to be part of onion network, then still "at the beginning of the onion route" means traffic leaves client machine unencrypted.

Reasons to correct:

1) Wikipedia tells us (article "Tor", section "Eavesdropping by exit nodes") data following out of onion network on Tor's exit nodes is indeed UNencrypted, but NOT at the beginning of onion network, so logical chain would be: data leaves client computer encrypted, travels through onion network encrypted and THE ONLY place it is unencrypted is way out of exit node.

2) www.torproject.org/overview (Tor's homepage) tells us data (traffic) leaves client computer encrypted (see diagrams).

So, taking into account 1) and 2) you may be right regarding you statement about plain-text traffic at the beginning of the onion route if:
- wiki doesn't say whole truth and Tor developers (or whatever site's authors) lie ;
- there is a mistake on Tor's homepage.

Why am i say about this? Why is this important? Because to my opinion, traffic encryption at the place when it leaves client computer is vital to guard against ISPs and authorities which can force ISPs to do anything (to provide data etc.). We don't know how do ISPs (would potentially) process our traffic, so it is extremely important they get nothing (encrypted data) --hope i'm right :)

People who will find out what is Tor from your article, should know truth about such important case like traffic encryption.

Regards,
Keiner

Tor and RSS

Uwe Hermann — Fri, 03 Apr 2009 01:45:41 +0200

As RSS consists of simple HTTP requests you can anonymize it just as easily as browser traffic, i.e. visiting websites.

Depending on what you mean with "RSS aggregator" you can then indeed anonymously read RSS feeds. This will work fine with e.g. Akregator, but not necessarily with other applications (untested by me), or web-based RSS aggregator (where you usually have to login, and thus immediately lose your anonymity).

HTH, Uwe.

Tor, RSS, and blogs - how does that work?

Anonymous — Thu, 02 Apr 2009 22:31:08 +0200

Can one remain anonymous when using the Tor bundle with a blog/RSS aggregator? For instance, will blog owners be able to see your information when your read their blog entries through a blog aggregator ? Will the 'others' (anyone watchin or snooping) be able to see your info & what blogs you read via your blog aggregator?

Tor

Uwe Hermann — Thu, 27 Nov 2008 01:16:52 +0100

Hi, depends on your OS I guess, but I'd start with a tutorial at the main Tor website. There are some GUIs and simple browser plugins for Tor, but I strongly suggest you try to learn about at least some of the technical details, otherwise it's very easy to accidentally spoil your anonymity without even noticing.

Complete anonymity is very hard to achieve with technical measures already, and the problem becomes even harder when you add a human in the mix. People tend to make lots of mistakes which can kill anonymity, even more so if the underlying tech details are unknown to them.

HTH, Uwe.

This article

Adam Carter — Wed, 26 Nov 2008 22:32:25 +0100

Plenty of detail but unfortunately it doesn't mean a thing to me - I am looking for a simple way to hisde my IP address, can you anke any suggestions where I should start - I'm a bit of an idiot when it comes to the techy side of computers.

I do a lot of my business online and much of it is concerned with Patents and Copyright issues. The more people see about the sites I visit, the more likely they are to try and undercut me or, worse still, steal ideas and plans before the Patents are granted and business is agreed.

Any suggestions where a dickhead like me should start looking for something simple that will do the job without me needing to figure out all the technical jargon.

I'd appreciate your suggestions.

Thanks, Adam Carter

tor Skype using Proxychains

Wednesday — Sat, 11 Oct 2008 18:16:44 +0200

You can tor Skype by using Proxychains: http://ubuntuforums.org/showthread.php?t=419528

Essentially, you're substituting FreeCap with Proxychains, same concept, different application.

Encryption

Ciridian — Wed, 30 Jul 2008 19:36:38 +0200

Hi,

Basically, I would like to encrypt and anonymize all the HTTP traffic from my computer to the actual site.
I am using Tor + Privoxy with the Torbutton plugin in Firefox 3.0.1. For what I understand, this combination guarantees encryption only in the tor network itself? If that is correct, what software (preferably under Ubuntu) can I use to encrypt the rest?

Thanks for your help,

Ciridian

Wow. Now this is some great

andreea — Fri, 13 Jun 2008 18:00:26 +0200

Wow. Now this is some great information. I could use this a lot in my work field. I can make some drug rehab programs on an idea i got from your article. Maybe we can 1do something together. I will continue reading you for more great ideas.

RefControl

Anonymous — Mon, 24 Mar 2008 16:37:05 +0100

Please also pimp RefControl

http://www.stardrifter.org/refcontrol/

"RefControl is an extension for Firefox that lets you control what gets sent as the HTTP Referer on a per-site basis."

Check your referrer (and other Tor information) with this page:
http://torcheck.xenobite.eu/

Cheers

HOWTO: Anonymous communication with Tor - some hints and some pitfalls [Update]

Uwe Hermann — Mon, 06 Mar 2006 10:20:45 +0100

Warning: Very long post ahead. You have been warned!

What?

Tor is a Free Software project (revised BSD license), developed by Roger Dingledine and Nick Mathewson, that creates an infrastructure for anonymous TCP communication.

From the project website:

Tor is a toolset for a wide range of organizations and people that want to improve their safety and security on the Internet. Using Tor can help you anonymize web browsing and publishing, instant messaging, IRC, SSH, and other applications that use the TCP protocol. Tor also provides a platform on which software developers can build new applications with built-in anonymity, safety, and privacy features.

Tor aims to defend against traffic analysis, a form of network surveillance that threatens personal anonymity and privacy, confidential business activities and relationships, and state security. Communications are bounced around a distributed network of servers called onion routers, protecting you from websites that build profiles of your interests, local eavesdroppers that read your data or learn what sites you visit, and even the onion routers themselves.

Tor also allows you to set up and/or use a so-called Tor hidden service, i.e., a server that offers some service (a website, ssh access, or similar) without revealing its IP to its users.

Why?

Why would you want to use Tor? Well, because you probably don't want anybody (neither state agencies, nor companies, nor "hackers", nor any other individuals or groups) to be able to record, analyze, and (ab)use information about your web browsing habits, or any other communication habits. For instance, you don't want Google to have a complete search-profile of you, which — even worse — might some day get in the hands of other parties. In the days of massive data retention you don't want all your electronic traces to be recorded, stored for ages, analyzed, and data-mined for dubious reasons and with even more dubious results and false conclusions drawn that might negatively affect you. If you're a human rights activist in China, you want anonymous communication. If you're a whistleblower, you want anonymous communication. The list is endless.

For securing your communications, so that nobody is able to sniff your emails, your chat messages, your passwords, your private documents and conversations, you use encryption. For communicating anonymously you can use Tor. Combine both, and you have secure and anonymous communication.

In case you're wondering whether criminals might abuse Tor, read the Tor Abuse FAQ. Short answer: yes, but if you're willing to break the law, you already have anonymity (open access points, stolen/prepaid mobile phones, etc.). You don't need Tor to do bad things if you're a criminal.

If you're one of those horrible "oh, but I don't have anything to hide" guys, consider this: Say you have a drug/alcohol problem and want to visit an anti-drugs/anti-alcohol website or forum for help. Would you want the whole world, your neighbors, your co-workers, your boss, to know that, or would you rather want to keep that a secret? Say you have AIDS and want to get information on the web? Or, to make the example even more dramatic: Would you want some random guys to be able to watch you while you fuck your wife? No? So you have something to hide after all, right?

My point is: Everyone has something to hide, even more, it is a basic human right to have the ability to hide something. It's called privacy.

How?

Tor implements a form of onion routing to, basically, push encrypted data through multiple Tor nodes (servers), before it reaches the final destination (e.g. a website). The result is that neither the website owner, nor a local eavesdropper, nor any single Tor server knows who requested that specific website, hence you are communicating anonymously. For more technical details, read the Tor overview and the Tor documentation pages.

In order to use Tor, you have to install and run a local Tor client/daemon (this is not necessarily a Tor server!). On Debian, type apt-get install tor, on other systems you can get the respective binary packages or download the sources and compile Tor yourself.

Usually Tor is used together with Privoxy, a configurable HTTP proxy that sanitizes your web-browsing experience by removing nasty banner ads, pop-ups, JavaScript, webbugs, cookies etc. etc. So: apt-get install privoxy.

After installing and starting Tor and Privoxy, you can now configure your webbrowser to use Privoxy as an HTTP proxy (see below), and Privoxy will in turn use Tor to anonymize your communication if you add "forward-socks4a / localhost:9050 ." to your /etc/privoxy/config.

Anonymizing various applications

Most (but not all) of the following information is also covered in the very useful Torify HOWTO in the Tor wiki (I will add the missing information there, ASAP). As I'm pretty paranoid, I have checked every single of these configurations with Ethereal to ensure that the traffic is really anonymized. However, if you are paranoid, you shouldn't trust me, but rather test this stuff for yourself!

Warning: DNS Leaks:
The biggest problem with many applications is that they leak DNS requests. That is, although they use Tor to anonymize the traffic, they first send a DNS request untorified in order to get the IP address of the target system. Then they communicate "anonymously" with that target. The problem: any eavesdropper with more than three brain cells can conclude what website you visited, if they see that you send a DNS request for rsf.org, followed by some "anonymous" Tor traffic. The solution: use Tor together with Privoxy, that prevents DNS leaks. Many non-HTTP-based applications are usually torified using a small tool called torify (e.g. by typing torify fetchmail), but often this approach has DNS leaking problems, see below.

Webbrowser: Firefox, Mozilla, Galeon, Konqueror, ...:
Most browsers can be torified by using Privoxy as an HTTP(S) proxy, i.e. using 127.0.0.1 as proxy host and 8118 as proxy port.
For example, to torify Firefox go to Edit -> Preferences -> General -> Connection Settings -> Manual proxy configuration and configure:
HTTP Proxy: 127.0.0.1 port 8118 SSL Proxy: 127.0.0.1 port 8118 FTP Proxy: 127.0.0.1 port 8118 SOCKS v5
For Konqueror, go to Settings -> Configure Konqueror -> Proxy -> Manually Specify the proxy settings -> Setup and configure:
HTTP Proxy: 127.0.0.1 port 8118 HTTPS Proxy: 127.0.0.1 port 8118 FTP Proxy: 127.0.0.1 port 8118
Warning: Although Privoxy doesn't support FTP, you should configure the browser to use Tor + Privoxy for FTP. By doing that, you get an error message when you try to access ftp:// URLs, but at least you don't send untorified traffic without noticing.
Warning: Firefox's "Live Bookmarks" (RSS feeds) are a problem if you switch from a torified to an untorified state sometimes (by switching or enabling/disabling the proxy). Firefox periodically requests all the feeds you're subscribed to. If you turn off Tor + Privoxy usage, they will be requested non-anonymously, and you won't even notice it! Solution: remove all "Live Bookmarks", or never switch to untorified browsing.
HTTP-based tools: lynx, links, w3m, wget, curl, ...:
Most other HTTP tools, such as wget, can be torified by setting the respective values for the http_proxy and HTTP_PROXY environment variables. Applications that don't honor http_proxy probably have a configuration option to set the HTTP proxy.
Add this to your ~/.bashrc or similar config-file:
http_proxy=http://127.0.0.1:8118/ HTTP_PROXY=$http_proxy export http_proxy HTTP_PROXY
Warning: links is a notable exception here. It does not honor the http_proxy environment variable! However, you can add http_proxy 127.0.0.1:8118 to your /etc/links.cfg and/or to your ~/.links/links.cfg. Or go to Setup -> Network Options and do the same there. Or use the -http-proxy 127.0.0.1:8118 command line option.
Instant Messaging: Gaim:
Go to Preferences -> Network -> Proxy and configure this:
Proxy type: Socks 5 Host: 127.0.0.1 Port: 9050
Gaim doesn't seem to leak DNS requests.
Debian: Apt:
Setting http_proxy is enough, as apt-get honors the http_proxy environment variable. But you can also add this line to your /etc/apt/apt-conf:
Acquire::http::Proxy "http://127.0.0.1:8118/";
apt-get doesn't seem to leak DNS requests.
Warning: This will only work for deb/deb-src lines in /etc/apt/sources.list that use HTTP, because Privoxy does not support FTP.
RSS-Reader: Akregator:
Which RSS feeds you are reading tells quite a lot about you, and it's probably an information some people or organizations would be very interested in, I imagine. So anonymizing your feed-reader is quite important, IMHO. Akregator (a KDE RSS-reader application) uses Konqueror internally, so if you have set Konqueror to use Tor + Privoxy as HTTP-proxy, Akregator is safe, too.
Akregator doesn't seem to leak DNS requests.
Podcast Client: iPodder/Juice:
Got to File -> Preferences -> Network settings and configure this:
Use a proxy server: enable Address: http://127.0.0.1 Port: 8118
iPodder/Juice doesn't seem to leak DNS requests.
Secure login: ssh:
In order to torify all your ssh communications (ssh, slogin, sftp, etc.), edit your /etc/ssh/ssh_config and/or ~/.ssh/config and add:
Host * ProxyCommand socat STDIO SOCKS4A:127.0.0.1:%h:%p,socksport=9050
This requires socat, so: apt-get install socat.
ssh doesn't seem to leak DNS requests.
Warning: Simply using torify ssh does not suffice, it leaks DNS requests!
Email: fetchmail:
Properly torifying fetchmail is pretty ugly. Basically, torify fetchmail should be enough (one would think), but that leaks DNS requests! All tips offered in the Torify HOWTO suffer from this problem. The ideal solution would be to use tor-resolve (a small utility that resolves DNS requests via the Tor network, and hence anonymously) before fetching the emails, but I haven't found a good and simple solution for that. What I do right now is to hardcode IP addresses in my ~/.fetchmailrc config-file and then use torify fetchmail, which doesn't leak DNS requests. However, it leads to some ugly "fetchmail: Server CommonName mismatch: foo.bar.com != xxx.xxx.xxx.xxx" warnings.
I always start fetchmail manually, often by clicking an icon in my IceWM toolbar. So I use the following line in my ~/.icewm/toolbar config-file:
prog Fetchmail fetchmail xterm -e torify fetchmail
Sometimes I invoke fetchmail from the command-line, too, so I have this alias in my ~/.bashrc:
alias fetchmail='torify fetchmail'

Warning: Just for the record: torify fetchmail alone (i.e. used with hostnames in ~/.fetchmailrc) does not suffice, it leaks DNS requests!
IRC: XChat:
Go to Settings-> Preferences -> Network -> Network setup -> Proxy server and configure:
Hostname: 127.0.0.1 Port: 9050 Type: Socks5
Then make sure you check the "Use a proxy server" checkbox in the preferences dialog of the IRC server you want to use.
XChat doesn't leak DNS requests.

You might also want to check out toraliases, a small shell script you can source from your ~/.bashrc file. It defines some functions and aliases that transparently direct the traffic of some (but not all!) programs through Tor.

Applications which cannot easily be torified

Anything not using TCP usually cannot be torified, as Tor only works for TCP.

Non-TCP traffic from tools like ping, host, dig, nslookup, nmap, traceroute and lots more: as Tor only supports TCP, you're out of luck. However, you can safely use web-frontends such as dnsstuff.com over Tor + Privoxy (if they don't block Tor users, that is).
whois: Although torify whois google.com leaks the DNS request for the whois-server (in this case whois.crsnic.net), it doesn't seem to leak the host you wanted to lookup. Can somebody confirm this? The safer method is to use a web-frontend, though.
FTP: Although torify ncftp works, it leaks DNS requests! I haven't yet found a way to fix this (help is appreciated!). I also tried a few other FTP clients, without luck.
GnuPG: Using gpg anonymously should work by using a proper http_proxy environment variable and by using a hidden Tor server as keyserver.
Add this to your ~/.gnupg/gpg.conf:
keyserver x-hkp://yod73zr3y6wnm2sw.onion keyserver-options honor-http-proxy broken-http-proxy
This works in theory. However, I noticed a problem: while gpg --recv-keys seems to work fine, gpg --refresh-keys leaks DNS requests! It seems GnuPG hard-codes the keyserver to keyserver.pgp.com in that case and leaks the DNS request for this domain name.
Sending email (SMTP): Not sure how to do this with Tor. Many Tor nodes block SMTP per default. A better solution is probably Mixmaster/Mixminion.
CVS, svn, Bittorrent/Azureus (untested HOWTO), usenet clients (pan, slrn), xmms: TODO. Haven't checked, yet.

Pitfalls to be aware of

Rule #1: Don't spoil your anonymity by being stupid!
IRC: Don't use nicks which hint at you, such as your real name, real-life nickname, acronyms which are known to "belong" to you or identify you. Don't use things like DCC that might reveal your real IP or real information about you. Disable all possibly "leaky" features/commands such as CTCP, VERSION requests, automatically accepting files from other IRC users, etc. etc.
Don't accidentally access Tor hidden server URLs in an untorified browser. For example, if you would try to access the fictitious hidden server abc1234.onion, this request would travel over the net unencrypted and untorified. An eavesdropper could sniff that, enable Tor on his computer, go to abc1234.onion, and would know what you wanted to look at.
Double-check that all applications you use don't leak DNS requests.
Do not only configure your ~/.foobarrc config-files but also the config-files in /etc. Otherwise you might eventually use wget, ssh, lynx or other tools as root (instead of your normal, non-privileged user account) resulting in untorified traffic!
Disable all "check for updates automatically", "notify upon new release" and similar "phoning home" features in all your applications. Most such features are probably not Tor-safe, i.e. will send/receive untorified traffic. Some candidates are Firefox, Adobe Acrobat reader, Gaim, and others.
Never, never, think that Tor encrypts your traffic! It does not! The person who runs a Tor exit node can easily sniff all plain-text traffic! Tor only anonymizes your traffic, but it can still be sniffed plain-text at the beginning and at the end of the onion route! So don't do any HTTP-auth, or plain-text password sending for e.g. POP3, telnet, and so on. Always use encryption in addition to Tor!
In general, spread only a minimum of information. Disable referrer sending (e.g. using Privoxy), disable cookies, kill webbugs (Privoxy), and so on.
Watch your language, especially in public forums or IRC. A linguist can probably easily figure out which country/region you're from if you speak/write broken English or use certain idioms or false friends. This might or might not be a problem for you, but it's something you should bear in mind.
If you're extra paranoid, you could set up your firewall to block all outgoing DNS traffic and force all applications to use Tor to resolve names. You could probably also block all outgoing non-Tor traffic...
Another good idea is probably carrying an Anonym.OS LiveCD with you, so you can have a (more) anonymous communication wherever you go.

More information

More information is available in the Tor documentation, the Tor wiki, and especially in the Tor FAQ. In addition, there's an IRC channel on Freenode (#tor), some slides and a video (torrent) about Tor you might find interesting. If you would like to help, you can run a Tor server, donate some money, or volunteer to do other things (code, debug, document, translate, and more).

That's it for now. I'm very grateful for comments and suggestions, especially for hints on how to anonymize more applications. Also, if you notice any dumb mistakes I made, please leave a comment.

Update 2006-03-07: Fixed typos, added link to the toraliases project (thanks Benjamin Schieder).
Update 2006-03-10: Fixed a whole bunch grammar errors, thanks Geoffrey Lewis Goodell for the patch!