Updated botnet likely cause of surge in Tor traffic

Posted by   Virus Bulletin on   Sep 5, 2013

New Tor version should help the network deal with increased traffic.

Sometimes a picture says more than a thousand words:

The graph shows the daily number of users of the Tor anonymity network over the past three years. As both the network and concerns over anonymity have grown, the usage has shown a slow but steady growth, with the occasional short peak. And then suddenly, in the third week of August this year, the number of users started to grow very quickly, resulting in a five-fold increase in barely two weeks.

Such a sharp increase cannot simply be explained by increased fears over surveillance, especially given that there was no noticeable increase in Tor usage directly following Edward Snowden's PRISM revelations.

Some have suggested that the release of PirateBrowser, a web browser designed to circumvent censorship that uses Tor, was the reason for the huge increase, but this seems unlikely: the browser was released well before the number of Tor users started to grow, and it uses the FoxyProxy Firefox plug-in - the use of which didn't see such a huge increase.

A more likely explanation would be that a botnet is responsible for the increased use of Tor.

Botnets using Tor for command and control communications aren't new. Neither are botnets that use Tor to hide the location of their nodes when performing a malicious activity: leaving comment spam on websites appears to be commonly done through Tor.

Researchers have been searching for evidence of such a botnet. Today, Fox-IT's Yonathan Klijnsma writes about a botnet that could well explain the surge in Tor users.

The malware he analysed isn't new and is known as 'Mevade' or 'Sefnit', while to those running it may be known as 'SBC'. Recently, coinciding with the increase in Tor users, it switched to Tor for its C&C communication. Both the size of the botnet and the particular Tor version used add to the belief that this is indeed what has caused the increase.

It is less clear what the purpose of the botnet is. Klijnsma suggests that the botnet - which he believes to originate in the former Soviet Union - may be used to load additional malware onto the system and that it (or parts of it) is offered for sale. He believes the ultimate motive is financial gain.

The latter may be a relief for many of Tor's supporters, who worried that this was a DDoS attack against the service itself, possibly by an entity that doesn't like the idea of people using online anonymity. The fact that, rather uniquely, there has been no increase in Tor users in Israel had already provided fuel for conspiracy theories.

While a botnet consisting of millions of users is clearly harmful for the Internet as a whole, it is particularly harmful for Tor, whose four thousands nodes could barely deal with the increased traffic. In a blog post for the project, Tor's Roger Dingledine explains how some improvements to the protocol have been made that should help the network deal better with the increase in traffic.

The natural next step after the discovery of a large botnet would be to attempt to take it down. Normally this would involve shutting down, or taking over, the botnet's command and control servers, but given their hidden nature, this will not be an easy task.

The anonymous nature of Tor also means that we will never be certain whether this particular botnet is responsible for the sharp increase in users. But assuming it is, I worry this isn't the last we have heard of it. Hopefully security researchers will find a way to shut down the botnet and thus help the Internet in general, and Tor in particular.

Posted on 5 September 2013 by Martijn Grooten

twitter.png
fb.png
linkedin.png
googleplus.png
reddit.png

 

Latest posts:

VB2018 preview: hacking cars

In recent years, car hacking has evolved from a mostly theoretical research field involving giggling researchers and scared journalists, to one that actually concerns car owners and manufacturers. On today's blog we preview two VB2018 papers, by…

Where are all the ‘A’s in APT?

In a guest blog post by VB2018 gold partner Kaspersky Lab, Costin Raiu, Director of the company's Global Research and Analysis Team, looks critically at the 'A' in APT.

VB2018 preview: commercial spyware and its use by governments

Today, we preview three VB2018 presentations that look at threats against civil society in general and the use of commercial spyware by governments for this purpose in particular.

VB2018 preview: Wipers in the wild

Today we preview the VB2018 paper by Saher Naumaan (BAE Systems Applied Intelligence) on the use of wipers in APT attacks.

VB2018 preview: IoT botnets

The VB2018 programme is packed with a wide range of security topics featuring speakers from all around the world. Today we preview two of them: one by Qihoo 360 researchers on tracking variants of Mirai and one by researchers from Bitdefender on the…

We have placed cookies on your device in order to improve the functionality of this site, as outlined in our cookies policy. However, you may delete and block all cookies from this site and your use of the site will be unaffected. By continuing to browse this site, you are agreeing to Virus Bulletin's use of data as outlined in our privacy policy.