Ramblings & ephemera

Russian bot herders behind massive increase in spam

From Ryan Naraine’s “‘Pump-and-Dump’ Spam Surge Linked to Russian Bot Herders” (eWeek: 16 November 2006):

The recent surge in e-mail spam hawking penny stocks and penis enlargement pills is the handiwork of Russian hackers running a botnet powered by tens of thousands of hijacked computers.

Internet security researchers and law enforcement authorities have traced the operation to a well-organized hacking gang controlling a 70,000-strong peer-to-peer botnet seeded with the SpamThru Trojan. …

For starters, the Trojan comes with its own anti-virus scanner – a pirated copy of Kaspersky’s security software – that removes competing malware files from the hijacked machine. Once a Windows machine is infected, it becomes a peer in a peer-to-peer botnet controlled by a central server. If the control server is disabled by botnet hunters, the spammer simply has to control a single peer to retain control of all the bots and send instructions on the location of a new control server.

The bots are segmented into different server ports, determined by the variant of the Trojan installed, and further segmented into peer groups of no more than 512 bots. This allows the hackers to keep the overhead involved in exchanging information about other peers to a minimum, Stewart explained.

… the attackers are meticulous about keeping statistics on bot infections around the world.

For example, the SpamThru controller keeps statistics on the country of origin of all bots in the botnet. In all, computers in 166 countries are part of the botnet, with the United States accounting for more than half of the infections.

The botnet stats tracker even logs the version of Windows the infected client is running, down to the service pack level. One chart commandeered by Stewart showed that Windows XP SP2 … machines dominate the makeup of the botnet, a clear sign that the latest version of Microsoft’s operating system is falling prey to attacks.

Another sign of the complexity of the operation, Stewart found, was a database hacking component that signaled the ability of the spammers to target its pump-and-dump scams to victims most likely to be associated with stock trading.

Stewart said about 20 small investment and financial news sites have been breached for the express purpose of downloading user databases with e-mail addresses matched to names and other site registration data. On the bot herder’s control server, Stewart found a MySQL database dump of e-mail addresses associated with an online shop. …

The SpamThru spammer also controls lists of millions of e-mail addresses harvested from the hard drives of computers already in the botnet. …

“It’s a very enterprising operation and it’s interesting that they’re only doing pump-and-dump and penis enlargement spam. That’s probably because those are the most lucrative,” he added.

Even the spam messages come with a unique component. The messages are both text- and image-based and a lot of effort has been put into evading spam filters. For example, each SpamThru client works as its own spam engine, downloading a template containing the spam and random phrases to use as hash-busters, random “from” names, and a list of several hundred e-mail addresses to send to.

Stewart discovered that the image files in the templates are modified with every e-mail message sent, allowing the spammer to change the width and height. The image-based spam also includes random pixels at the bottom, specifically to defeat anti-spam technologies that reject mail based on a static image.

All SpamThru bots – the botnet controls about 73,000 infected clients – are also capable of using a list of proxy servers maintained by the controller to evade blacklisting of the bot IP addresses by anti-spam services. Stewart said this allows the Trojan to act as a “massive distributed engine for sending spam,” without the cost of maintaining static servers.

With a botnet of this size, the group is theoretically capable of sending a billion spam e-mails in a single day.

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