On April 8, global law enforcement, with the assistance of Intel Security/McAfee, took down the Beebone botnet, which propagates a particularly tricky polymorphic worm.
Law enforcement and criminals often act like predators and prey, each evolving and adapting, trying to gain an advantage. A few have developed the ability to camouflage themselves by constantly changing their appearance. We are now seeing this type of adaptive, polymorphic behavior in malware, and it is our turn to respond and neutralize it.
Identifying a unique signature is one of the oldest methods of combating malware. But this worm -- W32/Worm-AAEH, also known as VObfus, VBObfus, Changeup, and other names -- tries to overcome signature-based detection by changing its form every time it moves to a new system and as often as six times per day within an infected system. We now have more than 5 million unique samples of W32/Worm-AAEH. The worm can detect sandboxes and antivirus software, block connections to security company websites, disable tools that try to terminate it, leverage encryption techniques, and dynamically change control server addresses and domain names. As a result, it has remained a threat since it was first discovered almost six years ago. The worm has been responsible for infecting tens of thousands of systems, and initial estimates from the sinkhole operation suggest that the botnet is considerably larger than our original estimates (more details to follow).
Although the polymorphic worm evades signature-based defenses, it is readily stopped with behavioral policies such as preventing programs from creating an AutoRun file, blocking file execution in user folders, and watching or blocking outbound connections on selected ports.
In March of last year, McAfee Labs built an automated monitoring system to mimic the communications between this worm and its hosts, helping us to reduce infections and understand its behavior. Details about that system can be found here.
Armed with information gathered through our monitoring system, we worked with a coalition of law enforcement agencies, the Shadowserver Foundation, and other security vendors to take down the botnet supporting this worm along with the crime ring behind it.
The takedown was led by the Dutch National High Tech Crime Unit. International engagement was coordinated through Europol’s European Cybercrime Centre (EC3), the FBI, and US-based representatives at the National Cyber Investigative Joint Task Force- International Cyber Crime Coordination Cell (IC4), along with additional intelligence from Kaspersky Lab. Collectively, we were able to seize and suspend the domains used by the criminal control servers, which were spread across Europe.
This type of operation demonstrates how critical collaboration is for the continued security of our computer systems. Our success was heavily dependent on the work and cooperation of multiple national and international law enforcement agencies, supported by detailed work and timely information from security vendors. Without working together, this botnet and the criminals behind it would still be in operation.