Thursday, February 22, 2024

Red Menshen APT Group Deploying BPFDoor in Linux Kernel

APTs Red Menshen expands targets to Linux and cloud servers, as seen in ransomware attacks on VMware ESXi, Mirai botnet variations, and cloud-focused stealers and crypto miners.

APT groups extend focus beyond Windows, signified by Sandworm’s attacks on Linux-based routers. Unlike cybercrime malware with broad targets, APT malware prioritizes persistent stealth and routine maintenance.

Red Menshen, an APT group active in the Middle East and Asia, continuously enhances the BPFDoor backdoor, utilizing Berkeley Packet Filter (BPF) to evade Linux and Solaris OS firewalls. 

Cybersecurity researchers at Trend Micro identify the Linux and Solaris variants as Backdoor.Linux.BPFDOOR and Backdoor.Solaris.BPFDOOR.ZAJE, respectively, with added monitoring and detection patterns.

Red Menshen advances BPF filters, increasing instructions six-fold, indicating active development and successful deployment of BPFDoor.

Workflow of BPFDoor

The intriguing technical aspect of BPFDoor lies in its kernel-level loading of packet filters, commonly known as BPF or LSF in Linux, representing the same underlying technology.

BPFDoor’s BPF filters enable backdoor activation with a single network packet, bypassing firewalls by leveraging the kernel’s BPF engine, and this rootkit-like capability sets it apart from typical backdoors.

BPFDoor variants employ classic BPF filters, with Linux samples using SO_ATTACH_FILTER and Solaris samples utilizing libpcap functions for runtime filter loading.

When a packet with the magic number arrives, BPFDoor connects back to the source IP, establishing a distinct identifier-based communication.

A privileged reverse shell is established by BPFDoor, enabling remote command execution by the attacker through a pipe connection to the infected machine’s shell.

Activation of BPFDoor backdoor (Source – TrendMicro)

The samples of BPFDoor across 2018-2022 feature a uniform BPF program accepting unique magic numbers for the following protocols:-

  • TCP
  • UDP
  • ICMP
BPF program instruction old (Source – TrendMicro)

The BPF program in these samples comprises 30 instructions, which measure the filter’s complexity, reads the report shared.

On the affected systems, there are three distinct packets that trigger the activation of the backdoor, and here below, we have mentioned them:-

  • UDP packet containing the magic number 0x7255 at the data field
  • ICMP ECHO (ping) packet containing the same 0x7255 magic number at the data field
  • TCP packet containing the magic number 0x5293 at the data field

Experts identified four telfhash-supported samples introducing a 4-byte magic number for TCP packets, resulting in a new BPF program with 39 instructions.

BPF program instruction New (Source – TrendMicro)

In 2023, three samples utilized an enhanced BPF program with 229 instructions, specifically validating ICMP packets as ICMP ECHO requests.

Targets of Red Menshen APT

Here below, we have mentioned the countries targeted using BPFDoor:-

  • Turkey
  • Hong Kong
  • Brazil

Here below, we have mentioned the industries targeted using BPFDoor:-

  • Telecommunication services
  • Financial services
  • Other services

Incorporating BPF bytecode into malware poses a new complicated hurdle for security experts. So, the BPFDoor’s evolving filters indicate threat actors’ efforts to enhance stealth and evade detection.

Updating rules and diving into BPF filter analysis promptly is advised for network defenders and malware analysts.


Latest articles

Beware of New AsukaStealer Steal Browser Passwords & Desktop Screens

An updated version of the ObserverStealer known as AsukaStealer was observed to be advertised as...

US to Pay $15M for Info About Lockbit Ransomware Operator Data

In a significant move against cybercrime, the U.S. government has announced a bounty of...

Earth Preta Hackers Abuses Google Drive to Deploy DOPLUGS Malware

Threat actors abuse Google Drive for several malicious activities due to its widespread use,...

Swiggy Account Hacked, Hackers Placed Orders Worth Rs 97,000

In a startling incident underscoring the growing menace of cybercrime, a woman's Swiggy account...

Beware of VietCredCare Malware that Steals businesses’ Facebook Accounts

A new cybersecurity threat targeting Facebook advertisers in Vietnam, known as VietCredCare, has emerged....

Google Chrome 122 Update Addresses Critical Security Vulnerabilities

Google has recently unveiled Chrome 122, a significant milestone for the widely used web...

New Malicious PyPI Packages Use DLL Sideloading In A Supply Chain Attack

Researchers have discovered that threat actors have been using open-source platforms and codes for...
Tushar Subhra Dutta
Tushar Subhra Dutta
Tushar is a Cyber security content editor with a passion for creating captivating and informative content. With years of experience under his belt in Cyber Security, he is covering Cyber Security News, technology and other news.

Live Account Takeover Attack Simulation

Live Account Take Over Attack

Live Webinar on How do hackers bypass 2FA ,Detecting ATO attacks, A demo of credential stuffing, brute force and session jacking-based ATO attacks, Identifying attacks with behaviour-based analysis and Building custom protection for applications and APIs.

Related Articles