Cybersecurity firm Deep Instinct has uncovered a previously undocumented variant of the Linux backdoor BPFDoor, known for its stealthiness and difficulty in detection.
The malware, associated with a Chinese threat actor called Red Menshen, targets telecom providers in the Middle East and Asia, aiming to establish persistent remote access to compromised environments. BPFDoor utilizes Berkeley Packet Filters (BPF) for network communications, enabling threat actors to execute code undetected and filter out unnecessary data.
The latest iteration of BPFDoor, named JustForFun, has retained its reputation as a highly elusive malware. It removes hard-coded indicators and incorporates encryption and a reverse shell for command-and-control communication.
Upon launch, BPFDoor configures itself to ignore operating system signals and sets up a packet sniffing socket to monitor incoming traffic with a specific Magic Byte sequence. This allows the malware to parse out commands from the traffic and establish an encrypted reverse shell session with a command-and-control server.
The sophistication and longevity of BPFDoor, which has operated undetected for years, highlight the increasing focus of threat actors on Linux systems due to their prevalence in enterprise and cloud environments.
In response to such threats, Google has introduced the eBPF fuzzing framework called Buzzer to enhance the security of the Linux kernel and ensure the safety of privileged sandboxed programs.
This testing approach has also led to the discovery of a security flaw (CVE-2023-2163) that allows arbitrary reading and writing of kernel memory, further emphasizing the importance of proactive security measures.
