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Northwave Cyber Security has found a sophisticated backdoor, LITTLELAMB.WOOLTEA, targeting Palo Alto Networks firewalls.
Northwave researcher claimed the backdoor was found during a forensic investigation of a compromised Palo Alto Networks device. Attackers exploited a recently disclosed vulnerability (CVE-2024-9474) to enter the system and deploy a malicious script called bwmupdate, which installed the backdoor. Northwave notes, “This backdoor is then executed using execve(), which fully replaces any running legitimate logd process with the malicious one.”
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LITTLELAMB.WOOLTEA operates stealthily by masquerading as a legitimate logging service. It maintains persistence by modifying the rc.local file and changing the RedHat package manager’s configuration to survive system upgrades.
The backdoor injects a dynamic library into the nginx process, altering the accept() function. This allows attackers to use a 48-byte “magic knock” for covert communication through existing open ports, making detection more difficult.
The backdoor’s functionalities include:
Reading and writing files on the target system.
Providing shell access for remote command execution.
Establishing single or multi-port network tunnels, enabling secure communication channels with other compromised nodes.
Setting up a SOCKS5 proxy for covert data transfer.
Northwave explains, “The backdoor supports running commands in a shell. Output from stdout or stderr is forwarded to the user… ” ensuring robust control over the compromised device.
The backdoor uses a flexible communication protocol that separates operator connections from device-to-device communications with unique identifiers, allowing for a structured command system across infected devices.
Although it’s not confirmed, the complexity of LITTLELAMB.WOOLTEA suggests a nation-state actor. Northwave said, “A suspected nation state threat actor gained entry to a Palo Alto network device through CVE2024-9474, shortly after details of the vulnerability were made public.”
Source: Northwave cybersecurity, securityonline
