Description

Cybersecurity experts have recently identified a sophisticated Python-based malicious program, dubbed the Anubis Backdoor, deployed by the well-known cybercriminal organization FIN7. This group, active for over eight years, has caused substantial financial losses worldwide, focusing primarily on the finance and hospitality industries. The Anubis Backdoor signifies a notable advancement in FIN7's methods, as it utilizes Python to create a concealed tool that mimics normal system operations. The initial method of compromise involves a seemingly harmless compressed file containing several Python scripts, including "conf.py." Research indicates these files are distributed through phishing attacks, demonstrating FIN7's ongoing use of social engineering. The "conf.py" script executes a multi-stage attack, employing robust encryption techniques like AES-CBC with padding, secure hashing with SHA-256, and Base64 encoding to conceal its malicious code. The script handles an obscured code string by segmenting and decoding it, decrypting the content, writing it to a temporary file for execution, and subsequently removing the file to minimize its trace on the compromised system. The Anubis Backdoor's primary functions involve network communication through standard HTTP ports, customizable server lists stored within the Windows Registry for sustained access, and command execution through Python's subprocess module. It includes a simple file upload system, enabling attackers to deploy additional malicious software onto compromised machines. The backdoor maintains its presence by storing its command-and-control settings within the Windows Registry, secured using AES-CBC encryption with a key derived from the agent’s unique identifier and the victim’s computer name. This approach ensures each compromised system has a unique encryption key, making decryption without specific environmental details extremely difficult.