Octopus Scanner: Java Build Tools and Malware

Alvaro Muñoz recently posted "The Octopus Scanner Malware: Attacking the open source supply chain" on the GitHub Security Lab site. I found this post to be interesting for a number of reasons, including its detailed coverage of how the Octopus Scanner malware works and how it was discovered, how the GitHub Security Incident Report Team (SIRT) went about addressing it, how it affected a popular Java IDE, and how GitHub works to detect and address risks to open source software deployed on its site.

Muñoz calls Octopus Scanner "an OSS supply chain malware" and writes that 26 GitHub-hosted open source projects "were backdoored by this malware." In the post, Muñoz describes in detail how Octopus Scanner works. The post in its entirety is worth reading, but here are some highlights describing Octopus Scanner:

• "Octopus Scanner malware is only interested in the pre-jar and post-jar tasks" of "a NetBeans project build."
• "The malware disguises itself as an ocs.txt file, but we can easily determine is is actually a Java Archive (JAR) file."
• "The malware also infected any JAR files that were available in the project, such as dependencies - not necessarily just build artifacts."
• "The octopus.dat payload is the binary that actually performs the NetBeans build infections."
• "cache.dat is responsible for backdooring the built classes so that when these classes get executed, they will infect the underlying system."
• Octopus Scanner is designed to target "UNIX-like systems", MacOS, and Windows.

I found the highly detailed approach to diagnosing Octopus Scanner's behavior in the GitHub post to be fascinating and insightful reading. It was especially insightful to see the tools and methods used to understand better how Octopus Scanner behaves. For example, they used ClassFileTransformer and "a Bytecode manipulation library such as Javassist or ByteBuddy to inject our analysis code" into the "class responsible for decrypting the blob ... right before it actually gets loaded into the JVM."

Besides the interesting details of how Octopus Scanner works and how it was discovered and researched, other interesting insights in this GitHub post are related to the risks open source builds face. Muñoz writes, "Infecting build artifacts is a means to infect more hosts since the infected project will most likely get built by other systems and the build artifacts will probably be loaded and executed on other systems as well." Muñoz adds, "In an OSS context, it gives the malware an effective means of transmission since the affected projects will presumably get cloned, forked, and used on potentially many different systems. The actual artifacts of these builds may spread even further in a way that is disconnected from the original build process and harder to track down after the fact."

Muñoz opens the post and concludes the post with some discussions about this and other attempts at sabotaging open source products and their builds. One chilling thought is included in the Conclusion: "Since the primary-infected users are developers, the access that is gained is of high interest to attackers since developers generally have access to additional projects, production environments, database passwords, and other critical assets. There is a huge potential for escalation of access, which is a core attacker objective in most cases."