- PRoot enables threat actors to bypass the system’s tools and the environment setup to avoid detection.
- The malicious filesystem, which includes everything needed, is created in the attackers’ system to avoid detection tools.
- Beyond the crypto mining use case, PRoot can be used in malware deployment and in facilitating persistence.
The Sysdig Threat Research Team warns users about an emerging threat. The team stated that threat actors are leveraging PRoot to expand the scope of their operations to multiple Linux distributions. PRoot is an open-source tool providing threat actors with a consistent operational environment across different Linux distributions. With its emulation capabilities, it also enables the building of malware on other architectures.
Bring your own file system
The post-exploitation technique is called BYOF, which stands for “bring your own file system”. It is being used by hackers, especially when they don’t have a full understanding of the environment ahead of time, or lack the resources to change their tools for the environment. On the other hand, PRoot was created to improve compatibility, to simplify things for administrators. PRoot relies on two elements:
- PTRACE: An unprivileged syscall usually available in Linux distributions that can monitor, control, and manipulate other processes.
- QEMU: A tool that can emulate programs built for different architectures through dynamic binary execution; an abbreviation of Quick EMUlation.
The attack starts with creating a malicious filesystem to be deployed, including everything that the operation needs to be successful. The preparation in the early stages enables all of the tools to be downloaded, configured, or installed on the attacker’s system.
The archives are placed on well-known storage platforms for the attack. When a hacker gains access to a system, the filesystem is downloaded along with PRoot, thus, it doesn’t need any additional external files or libraries. Then the filesystem was unpacked and the attacker runs the proot executable. PRoot offers a threat actor a number of benefits:
- PRoot easily delivers malicious code by packing it into a filesystem.
- The attack is more scalable since the commands are more likely to succeed.
- An attacker can define different attack paths. Installing and executing a miner is only one of the scenarios; it is also possible to set up persistence mechanisms or run other malware (DDoS, crypto locker, etc.).
- The architecture of the compiled malicious executables is irrelevant.
« Attackers’ post-exploitation techniques and paths are always improving and evolving to evade detection during the setup and execution phases in the victims’ environment.
The discovery of PRoot allowing attackers to bypass a target system’s tools and skip the environment setup and execution is a powerful option for defense evasion. Beyond the cryptomining use case, PRoot can be used in malware deployment and in facilitating persistence. It removes attacker’s concerns with targets’ varying architecture types and provides a greater attack scale and success rate.
Thus, it is instrumental for your company’s security operations to have a runtime detection layer, such as Falco, that can detect this behavior. Ensure you can observe this type of threat to reduce your risk of exploitation, the costs of cryptomining, and attacker persistence on your network. »