Diamorphine Rootkit Exploiting Linux Systems In The Wild

Threat actors exploit Linux systems because they are prevalent in organizations that host servers, databases, and other important resources. 

Exploiting vulnerabilities in Linux systems allows attackers to gain access to sensitive data, disrupt services, or deploy malware. 

Besides this, the open-source nature of Linux can sometimes expose the security flaws that hackers can exploit.

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Cybersecurity analysts at Avast recently identified that the Diamorphine rootkit is actively exploiting Linux systems in the wild.

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Diamorphine Rootkit Linux Systems

Code reuse makes it possible to find new viruses more effectively and trace old ones. Diamorphine has become a popular Linux rootkit that may be used in many kernel versions with different architectures.

Another variant, which had not been identified yet, was discovered in March 2024. It pretended to be an x_tables module for kernel 5.19.17. 

Avast analysis showed that Diamorphine has some core attributes, including process hiding, module hiding, root escalation, and other payloads.

A few additions are breaking Diamorphine via xx_tables messages and sending magical packets to run arbitrary OS commands.

To test this Diamorphine variant impersonating Netfilter’s x_tables module for kernel 5.19.17, Ubuntu 22.04 (Jammy) is a suitable distribution matching the symbol versions. 

It creates the xx_tables device for user-kernel communication, with the “g” function handling write operations by copying data from userspace via copy_from_user. 

If “exit” is sent, exit_function restores the system and unloads the module. 

New functionality supports IPv4/IPv6 “magic packets” containing encrypted strings like “whitehat.” These packets trigger the execution of arbitrary commands extracted from them after passing netfilter_hook_function checks in nested a,b,c,d,e,f calls.

Here below, we have mentioned all the functions that are performed by the exit_ function:-

• It destroys the device created by the rootkit.
• It destroys the struct class that was used for creating the device.
• Deletes the cdev (character device) that was created.
• Unregisters the chrdev_region.
• Unregisters the Netfilter hooks implementing the “magic packets“.
• Finally, it replaces the pointers with the original functions in the system_calls table.

New undetected Linux kernel rootkits implementing “magic packet” functionality for arbitrary command execution, such as Syslogk, AntiUnhide, Chicken, and this updated Diamorphine variant, continue to be discovered. 

The latest Diamorphine adds a device interface to unload the rootkit module and “magic packet” handling to trigger the execution of any commands on the compromised system. 

Ongoing collaboration aims to provide the highest protection against these stealthy kernel-level threats.

Recommendations

Here below, we have mentioned all the provided recommendations:-

• Stay vigilant for new kernel rootkits that are utilizing “magic packets” in order to implement remote code execution.
• Stay up-to-date with new rootkit versions that introduce harmful functionalities such as offload interfaces and packet command triggers.
• Prefer solid prevention strategy against kernel threats through collaborative security work and advanced detection.
• Strengthen your systems’ defenses to protect them from hidden kernel-level malware and illegal entry.
• Establish tough network surveillance and filtering for possible communication using a “magic packet” by a rootkit.

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