A piece of banking malware that researchers have been keeping an eye on is adding more sophisticated capabilities to stay hidden on victims' PCs, according to the vendor Seculert.
Carberp, which targets computers running Microsoft's Windows OS, was discovered last October by several security companies and noted for its ability to steal a range of data as well as disguise itself as legitimate Windows files and remove antivirus software. It has been billed as a rival to Zeus, another well-known piece of malware.
Carberp communicates with a command-and-controller (C&C) server using encrypted HTTP Web traffic. Previous versions of Carberp encrypted that traffic using RC4 encryption but always used the same encryption key.
Using the same key meant it was easier for intrusion protection systems to analyze traffic and pick out possible communication between the infected Carberp computers and the C&C servers, said Aviv Raff, CTO and co-founder of Seculert. Seculert runs a cloud-based service that alerts its customers to new malware, exploits and other cyberthreats.
A new version of Carberp is mixing it up, using a randomly different key when it makes an HTTP request, said Raff. When it uses the same key, there are some static patterns that can be detected. Even Zeus, which is begrudgingly respected for its high-quality engineering, uses the same key that is embedded in the malware.
"Most network based security solutions are using traffic signatures to detect bots trying to connect to the C&C," Raff said. "This new feature is used to evade this type of detection and make it hard and almost impossible to create such signatures."
Seculart has posted a writeup about Carberp.
Carberp has also expanded the scope of the victims it seeks to infect. The latest version is targeted users in Russian-speaking markets, Raff said. Previous versions targeted banks in the Netherlands and the U.S., he said.