The Inside Story of the Kelihos Botnet Takedown
A botnet is corralled:
Earlier this week, Microsoft released an announcement about the disruption of a dangerous botnet that was responsible for spam messages, theft of sensitive financial information, pump-and-dump stock scams and distributed denial-of-service attacks.
Kaspersky Lab played a critical role in this botnet takedown initiative, leading the way to reverse-engineer the bot malware, crack the communication protocol and develop tools to attack the peer-to-peer infrastructure. We worked closely with Microsoft’s Digital Crimes Unit (DCU), sharing the relevant information and providing them with access to our live botnet tracking system.
A key part of this effort is the sinkholing of the botnet. It’s important to understand that the botnet still exists – but it’s being controlled by Kaspersky Lab. In tandem with Microsoft’s move to the U.S. court system to disable the domains, we started to sinkhole the botnet. Right now we have 3,000 hosts connecting to our sinkhole every minute. This post describes the inner workings of the botnet and the work we did to prevent it from further operation.
Let’s start with some technical background: Kelihos is Microsoft’s name for what Kaspersky calls Hlux. Hlux is a peer-to-peer botnet with an architecture similar to the one used for the Waledac botnet. It consists of layers of different kinds of nodes: controllers, routers and workers. Controllers are machines presumably operated by the gang behind the botnet. They distribute commands to the bots and supervise the peer-to-peer network’s dynamic structure. Routers are infected machines with public IP addresses. They run the bot in router mode, host proxy services, participate in a fast-flux collective, and so on. Finally, workers are infected machines that do not run in router mode, simply put. They are used for sending out spam, collecting email addresses, sniffing user credentials from the network stream, etc.