Cutwail botnet sent 1.7 trillion spam messages

Posted by   Virus Bulletin on   Mar 18, 2011

Operators made several million through botnet.

Researchers from The Last Line of Defense and universities in Bochum and Santa Barbara have shared some insight into the workings of the Cutwail botnet (also known as Pushdo) after having managed to gain access to its command and control (C&C) servers.

Using the logs of the C&C servers to which they had access (estimated to represent between half and two-thirds of the total number of active Cutwail servers), the researchers were able to ascertain an exact figure for the number of spam emails sent. Between June 2009 and August 2010, these servers sent over 1.7 trillion spam messages - an average of well over 3 billion per day.

The fact that spammers have begun to care not just about sending but also about delivering messages could also be seen from the servers' logs, which recorded that 500 billion messages (just over 30% of the messages sent) were accepted during the SMTP transaction. Blacklists, invalid addresses and SMTP errors are likely to be the main reasons for the other messages not being delivered.

Even with only a small fraction of these 500 billion messages getting past spam filters and reaching users' inboxes, it is not surprising that the owners of Cutwail made a lot of money through renting out parts of their botnet. The researchers estimated the profits to be between $1.7 and $4.2 million.

As a result of the researchers' work the C&C servers to which they had access were taken offline, causing the amount of spam sent through Cutwail to drop significantly. However, the researchers showed little optimism about the long-term success of their efforts, suggesting the money to be made and the low risk, will always make crooks build ever more resilient botnets.

The full paper, which will be presented at the LEET '11 workshop later this month can be found here (PDF), while Threatpost has a long summary here.

Readers may also be interested in the article (requires free registration) by Fortinet's Kyle Yang on the Cutwail botnet, which was published in Virus Bulletin in February 2010.

Posted on 18 March 2011 by Virus Bulletin

twitter.png
fb.png
linkedin.png
hackernews.png
reddit.png

 

Latest posts:

VB2018 paper: Lazarus Group: a mahjong game played with different sets of tiles

The Lazarus Group, generally linked to the North Korean government, is one of the most notorious threat groups seen in recent years. At VB2018 ESET researchers Peter Kálnai and Michal Poslušný presented a paper looking at the group's various…

Book your VB2019 ticket now for a chance to win a ticket for BSides London

Virus Bulletin is proud to sponsor this year's BSides London conference, which will take place next week, and we have a number of tickets to give away.

First 11 partners of VB2019 announced

We are excited to announce the first 11 companies to partner with VB2019, whose support will help ensure a great event.

VB2018 paper: Fake News, Inc.

A former reporter by profession, Andrew Brandt's curiosity was piqued when he came across what appeared at first glance to be the website of a small-town newspaper based in Illinois, but under scrutiny, things didn’t add up. At VB2018 he presented a…

Paper: Alternative communication channel over NTP

In a new paper published today, independent researcher Nikolaos Tsapakis writes about the possibilities of malware using NTP as a covert communication channel and how to stop this.

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.