Researchers at Dell SecureWorks and Palo Alto Networks have teamed up to analyze the Ramdo click-fraud malware, a threat that has been infecting computers around the world since late 2013.
Ramdo, also known as Redyms, helps cybercriminals make a profit by silently clicking on online ads from infected systems. The malware is also capable of downloading and installing additional malicious software on infected devices.
Once it infects a computer — primarily by leveraging exploit kits such as Angler, RIG and Magnitude — Ramdo checks for the presence of sandboxes and virtual machines, which could indicate that the threat is being analyzed by researchers. If these types of applications are not detected, the malware creates a new Windows process and injects a malicious DLL into it.
The malware then contacts its command and control (C&C) server and downloads a copy of the Chromium Extended Framework, which allows users to embed Chromium-based browsers in other applications. This browser is used to navigate to pages containing advertisements.
However, the attackers have designed the malware to access the ads via a specially designed search portal instead of navigating to them directly. By accessing websites from a search portal that displays links to sponsored ads, website analytics tools are tricked and advertisers are led to believe their ads were accessed by a user conducting a Web search instead of a bot.
Ramdo checks for the presence of virtual environments by analyzing the CPU to see if it’s running in hypervisor mode. It also checks for the presence of a sandbox by searching for specific strings.
Unlike other malware, Ramdo doesn’t completely stop if it detects a sandbox or a virtual machine. Instead, it changes its behavior and generates special command and control (C&C) domains that the malware connects to.
By using this technique, attackers can not only throw researchers off track, but they can also learn when someone is trying to analyze their malware.
Experts determined that, starting with June 2015, Ramdo has been using HTTPS to communicate with its C&C servers, whose domains are generated using a domain generation algorithm (DGA).
Sinkholing Ramdo C&C servers revealed that most Ramdo infections are in the United States, followed by Germany, Australia and Japan. Over the course of seven days, more than 70,000 connections were made to the sinkholes from roughly 1,000 unique IP addresses, 434 of which were located in the US.
Based on their analysis, Palo Alto Networks and Dell SecureWorks concluded that while Ramdo is not particularly sophisticated, its operators are actively working on implementing new features to avoid detection and prevent analysis.