SAN FRANCISCO - RSA CONFERENCE 2012 – On Tuesday, Atlanta-based Damballa released the results of a study into the techniques used by six known malware families to avoid detection. These methods, commonly known as evasion techniques, include the use of domain generation algorithms, or DGAs, which allow the malware to avoid blacklists, signature filters, and reputation-based detection systems.
Most of the security world knows the concept of DGAs as fluxing, or the ability to use multiple FQDNs and tie them to a single IP or C&C. According to Damballa, there are six families using these methods, including the newest Zeus variant, Bamital, BankPatch, Bonnana, Expiro.Z, and Shiz. The oldest, BankPatch, has been using DGAs for more than two years.
"While DGAs are not new, the rate at which they are being adopted and their ability to elude the scrutiny of some of the most advanced malware analysis professionals should be of great concern to incident response professionals," stated Gunter Ollmann, vice president of research for Damballa.
The concept of DGAs is simple enough, but incredibly stealthy, Damballa said. Malware that has infected an endpoint device is programmed with an algorithm that uses a 'seed' value, like the current date, to generate potentially hundreds of seemingly random domain names that all attempt to resolve to an IP address.
Nearly all of the domain names will result in a 'non-existent' domain message (NXDomain). Only one or a few will actually resolve to an IP address. The criminal operator, knowing the nature of the algorithm and the seed that will be used that day, will register only one (or a few) of the domains and have them resolve to his C&C infrastructure. The next day the cycle repeats. The domains used for the previous day's connection are discarded, meaning the domain names are 'thrown away,' and even if detected, would be meaningless in stopping the threat or discovering the criminal C&C.
“We have found that the security community as a whole has insufficiently or only partially analyzed the network behaviors of DGA-capable malware. For one, some advanced malware is using DGA as a secondary connection technique when the primary technique, let's say peer-to-peer, has failed. Those charged with protecting the enterprise that have detected or blocked the obvious primary connection technique have failed to counter the back-up technique, and the malware can then successfully locate the C&C using DGAs,” Ollmann added.
A report on the use of DGAs can be read here.
In related news, Damballa released the Failsafe MicroSensor this week, an alternative to the company's existing 1U Sensor. Damballa Failsafe hunts for hidden infections by correlating a variety of observed network behaviors that indicate when malware-infected devices (PCs, Macs, servers, smartphones, iPads, etc.) are communicating with criminals.
Additionally, Damballa has integrated Failsafe with HP ArcSight Logger for capturing real-time streams of DNS logs.