What we learned by unpacking a recent wave of Imminent RAT infections using AMP

This blog post was authored by Chris Marczewski

Cisco Talos has been tracking a series of Imminent RAT infections for the past two months following reported data from Cisco Advanced Malware Protection’s (AMP) Exploit Prevention engine. AMP successfully stopped the malware before it was able to infect the host, but an initial analysis showed a strong indication that stages exist before the deployment of the RAT. Surprisingly, the recovered samples showed no sign of Imminent RAT, but instead a commercial grade packer.

This was a series of attacks engineered to evade detection and frustrate analysis. From the outside, we have a commercially available, yet affordable packer called “Obsidium” that has been used in the past to protect the intellectual property of some legitimate software vendors. The payload results in a RAT called Imminent that has also been used previously for legitimate purposes. Imminent is a commercially available RAT that retails for $25 to $100, depending upon the size of the customer’s expected user base. While it is not intended for malicious use, in this case, its detection suggested otherwise.

Although a Potentially Unwanted Application (PUA) detection approach could suffice, not everyone enables blocking of PUAs. We have other technologies in place, such as the Exploit Prevention engine, that are well-suited to detecting such threats. We hope that after reading this research, you’ll have a better understanding of not only what it takes to investigate an attack using a complex packer, but also how AMP is equipped to stop such attacks that planned on successfully evading static detection or thwarting the benefits of dynamic analysis from a malware sandbox.