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Launching Attacks via TOR Re: Hacker strikes through student's router

They are probably referring to articles like the following:


Launching Attacks via Tor <http://dhanjani.com/archives/000085.html>

July 10, 2005

I have written about Tor before <http://dhanjani.com/archives/000069.html>. In my opinion, the Tor project <http://tor.eff.org/index.html> is an excellent effort towards protecting online privacy. I routinely use the Tor network, and it works well for me.

I believe that the merits of a project like Tor outweigh the channels of abuse it may grant malicious users. However, these channels of abuse do exist, and they cannot be ignored: if a malicious entity wants to scan or launch your network via the Internet, he or she can do this via the Tor network. This will make it incredibly difficult for you to track down the source of the attacks.

In order to demonstrate this, I setup a host on the Internet that I wanted to scan from my home network using the Nessus vulnerability scanner <http://nessus.org/>. Before an attacker can exploit a specific vulnerability, he or she will want to test the presence of the vulnerability using a scanner such as Nessus. Here are the steps I followed to launch the Nessus scan via Tor:

1) Install and Setup Tor <http://tor.eff.org/download.html>.

2) Download desproxysocat <http://www.dest-unreach.org/socat/> (Thanks Chris!). This tool will allow us to setup a local TCP listener that will tunnel connections via the Tor SOCKS server (listening on port 9050).

Let us assume that the IP address of the host I wanted to scan was (yes I know this is non-routable over the Internet, but I don’t want to publish the real IP address of my host). I invoked |socat| like this:

|./socat TCP4-LISTEN:8080,fork SOCKS4:,
The above command causes |socat| to listen on port 8080, and tunnel all incoming connections to (port 80) via the Tor SOCKS server.

[Updated July 12, 2005. Step 3 is not applicable now].
3) Configure |privoxy| to allow HTTP CONNECT requests via port 80. By default, only port 443 is allowed. To do this, configure your web browser to use |privoxy| as the HTTP proxy ( 81118) and browse to http://config.privoxy.org/show-status. Click on the "Edit" button next to the applicable "default.action" file, and choose the "Enable" radio button on the left side of “limit-connect”. Enter “80, 443” in the edit box and click on "Submit".

4) Install and configure Nessus <http://www.oreillynet.com/pub/a/security/2004/04/22/nessus.html>.

5) Launch a Nessus scan against port 8080. Configure Nessus to limit the scan to port 8080 in the “Scan Options” tab.

Here are some of the entries in my Apache log that were a result of the scan:

| - - [10/Jul/2005:17:29:56 -0700] "GET /Agents/ HTTP/1.1" 404 205 "-" "Mozilla/4.75 [en] (X11, U; Nessus)" - - [10/Jul/2005:17:29:56 -0700] "GET /cgi-bin/viewpic.php?id=7&conversation_id=<script>foo</script>&btopage=0 HTTP/1.1" 404 217 "-" "Mozilla/4.75 [en] (X11, U; Nessus)" - - [10/Jul/2005:17:29:57 -0700] "GET /index.php?err=3&email=<script>foo</script> HTTP/1.1" 404 207 "-" "Mozilla/4.75 [en] (X11, U; Nessus)" - - [10/Jul/2005:17:29:57 -0700] "GET /scripts/fom/fom.cgi?cmd=<script>foo</script>&file=1&keywords=nessus HTTP/1.1" 404 217 "-" "Mozilla/4.75 [en] (X11, U; Nessus)" - - [10/Jul/2005:17:29:58 -0700] "GET /scripts/viewpic.php?id=7&conversation_id=<script>foo</script>&btopage=0 HTTP/1.1" 404 217 "-" "Mozilla/4.75 [en] (X11, U; Nessus)" - - [10/Jul/2005:17:29:58 -0700] "GET /Album/ HTTP/1.1" 404 204 "-" "Mozilla/4.75 [en] (X11, U; Nessus)" - - [10/Jul/2005:17:29:59 -0700] "GET /fom/fom.cgi?cmd=<script>foo</script>&file=1&keywords=nessus HTTP/1.1" 404 209 "-" "Mozilla/4.75 [en] (X11, U; Nessus)" - - [10/Jul/2005:17:29:59 -0700] "GET /cgi-bin/wiki.pl?<script>foo</script> HTTP/1.1" 404 213 "-" "Mozilla/4.75 [en] (X11, U; Nessus)"|

The IP address represents the host that is the last onion router in the random circuit that was setup by the Tor software (NOTE: I don't want to publish the actual IP address of the last onion router that I noticed in my logs, so is a place holder to serve as an example). Given the design of Tor, it would be extremely difficult (if not impossible) to determine the source IP address (i.e. my IP address - and not the IP address of the last onion router). The above instructions can also be used to exploit software flaws (using tools such as Metasploit <http://www.metasploit.com/>) in order to anonymously execute arbitrary commands on vulnerable hosts.

I am a big fan of the Tor project. However, potential attackers who may want to hide their tracks may abuse the anonymity granted by Tor. The aim of this post is to shed light on this fact, and I hope it is helpful to administrators are effected by attacks that seem to originate from a source that is a onion router in reality.