In the ever-evolving landscape of cybersecurity, new threats emerge almost daily, challenging the defenses of organizations worldwide. One such threat that has recently come to light is a sophisticated malware toolkit known as Decoy Dog. This largely undetected toolkit has been operational for at least a year, primarily in cyber intelligence operations. Its unique reliance on the Domain Name System (DNS) for command and control activity sets it apart from other malware.
Decoding Decoy Dog
Decoy Dog is a highly sophisticated toolkit that has managed to stay under the radar for a significant period. Its origins and operators remain unclear, but researchers at Infoblox, a DNS-focused security vendor, believe that four distinct actors are developing and wielding it for highly-targeted operations. The observed activity of Decoy Dog is primarily confined to Russia and Eastern Europe, with indications that it may be related to Russia’s invasion of Ukraine.
The toolkit was discovered in early April when Infoblox specialists detected anomalous DNS beaconing activity from several domains acting as command and control servers for the malware. While the toolkit’s operators did not cease activity after Infoblox announced their discovery, they did make significant changes to its structure and functionality.
The Evolution of Decoy Dog
Decoy Dog is based on Pupy, an open-source post-exploitation remote access trojan (RAT). However, it is not merely a clone of Pupy but a significant upgrade. It uses Python 3.8, while Pupy was written in Python 2.7, and requires Python 3.8 for operation. This upgrade has led to numerous improvements, including better compatibility with Windows and enhanced memory operations.
One of the most notable enhancements is the expansion of the communication vocabulary in Pupy. Decoy Dog has added multiple communication modules, allowing it to respond to replays of previous DNS queries and wildcard DNS requests. This is a significant departure from Pupy, which does not have these capabilities.
Furthermore, Decoy Dog has added the ability to run arbitrary Java code by injecting it into a JVM thread. This feature, combined with methods to maintain persistence on a victim device, makes Decoy Dog a formidable threat in the hands of skilled operators.
The Operators Behind Decoy Dog
Infoblox initially identified three distinct operators of Decoy Dog, each responding differently to the company’s disclosure in April. A fourth operator was discovered after the completion of the current Infoblox report. Each operator appears to have unique tactics, techniques, and procedures (TTPs), although they all respond to queries that match the format for Decoy Dog or Pupy.
One of the operators has the most advanced version of Decoy Dog seen in public repositories. This group’s clients connect to the controller claudfront[.]net, indicating a high level of sophistication and capability.
The Targets of Decoy Dog
Based on passive DNS traffic analysis, it’s challenging to determine an accurate number of Decoy Dog clients. However, the largest number of active concurrent connections that Infoblox observed on any one controller was less than 50, and the smallest was four. This suggests that the number of compromised devices is less than a few hundred, indicating a very small set of targets. This is typical of an intelligence operation, which often focuses on high-value targets rather than widespread infection.
The Future of Decoy Dog
The operations of Decoy Dog remain a mystery in terms of their purpose and handlers. While Infoblox has done a commendable job of uncovering the toolkit using DNS data, further research is required to determine the targets, the initial compromise method, and how the actors move within the network.
In the face of this threat, defenders must consider that IP addresses in both Decoy Dog and Pupy represent encrypted data, not real addresses used for communication. They should also focus on DNS queries and responses, as they can help track the malware activity. However, the communication volume is low, and a large log history is needed to track the communication effectively.
The emergence of Decoy Dog underscores the importance of continuous vigilance in the cybersecurity landscape. As malware toolkits become more sophisticated, so too must our defenses. Understanding the nature of these threats, their origins, and their operations is the first step in building effective countermeasures. As we continue to unravel the mystery of Decoy Dog, we gain valuable insights that can help us prepare for and respond to future threats.
The cybersecurity community must continue to collaborate and share knowledge to stay ahead of these threats. Only through collective effort can we hope to safeguard our digital world against the ever-evolving threats posed by sophisticated malware like Decoy Dog.