Schneier on Security

The Nugache Worm/Botnet

I’ve already written about the Storm worm, and how it represents a new generation of worm/botnets. And Scott Berinato has written an excellent article about the Gozi worm, another new-generation worm/botnet.

This article is about yet another new-generation worm-botnet: Nugache. Dave Dittrich thinks this is the most advanced worm/botnet yet:

But this new piece of malware, which came to be known as Nugache, was a game-changer. With no C&C server to target, bots capable of sending encrypted packets and the possibility of any peer on the network suddenly becoming the de facto leader of the botnet, Nugache, Dittrich knew, would be virtually impossible to stop.

[…]

Nugache, and its more famous cousin, the Storm Trojan, are not simply the next step in the evolution of malware. They represent a major step forward in both the quality of software that malware authors are producing and in the sophistication of their tactics. Although they’re often referred to as worms, Storm and Nugache are actually Trojans. The Storm creator, for example, sends out millions of spam messages on a semi-regular basis, each containing a link to content on some remote server, normally disguised in a fake pitch for a penny stock, Viagra or relief for victims of a recent natural disaster. When a user clicks on the link, the attacker’s server installs the Storm Trojan on the user’s PC and it’s off and running.

Various worms, viruses, bots and Trojans over the years have had one or two of the features that Storm, Nugache, Rbot and other such programs possess, but none has approached the breadth and depth of their feature sets. Rbot, for example, has more than 100 features that users can choose from when compiling the bot. This means that two different bots compiled from an identical source could have nearly identical feature sets, yet look completely different to an antivirus engine.

[…]

As scary as Storm and Nugache are, the scarier thing is that they represent just the tip of the iceberg. Experts say that there are several malware groups out there right now that are writing custom Trojans, rootkits and attack toolkits to the specifications of their customers. The customers are in turn using the malware not to build worldwide botnets a la Storm, but to attack small slices of a certain industry, such as financial services or health care.

Rizo, a variant of the venerable Rbot, is the poster child for this kind of attack. A Trojan in the style of Nugache and Storm, Rizo has been modified a number of times to meet the requirements of various different attack scenarios. Within the course of a few weeks, different versions of Rizo were used to attack customers of several different banks in South America. Once installed on a user’s PC, it monitors Internet activity and gathers login credentials for online banking sites, which it then sends back to the attacker. It’s standard behavior for these kinds of Trojans, but the amount of specificity and customization involved in the code and the ways in which the author changed it over time are what have researchers worried.

[…]

“I’m pretty sure that there are tactics being shared between the Nugache and Storm authors,” Dittrich said. “There’s a direct lineage from Sdbot to Rbot to Mytob to Bancos. These guys can just sell the Web front-end to these things and the customers can pick their options and then just hit go.”

See also: “Command and control structures in malware: From Handler/Agent to P2P,” by Dave Dittrich and Sven Dietrich, USENIX ;login:, vol. 32, no. 6, December 2007, and “Analysis of the Storm and Nugache Trojans: P2P is here,” Sam Stover, Dave Dittrich, John Hernandez, and Sven Dietrich, USENIX ;login:, vol. 32, no. 6, December 2007. The second link is available to USENIX members only, unfortunately.

Tags: academic papers, banking, botnets, fraud, malware, spam

Posted on December 31, 2007 at 7:19 AM • 23 Comments