Description

Sophos recently uncovered a Nitrogen malware operation that uses Google and Bing search advertisements to promote fake software websites in order to trick unwary users into downloading malicious payloads such as Cobalt Strike and ransomware. Nitrogen's ultimate purpose is to provide threat actors with initial access to business networks, allowing them to steal data, conduct cyberespionage, and eventually spread the BlackCat/ALPHV ransomware. Notably, the campaign primarily targets North American technology and non-profit groups. The attackers imitate well-known software titles such as AnyDesk, Cisco AnyConnect VPN, TreeSize Free, and WinSCP to entice users The campaign begins as individuals use Google or Bing to search for popular software products such as AnyDesk, WinSCP, Cisco AnyConnect, and TreeSize Free. Users are led to hijacked WordPress hosting websites that closely resemble official software download sites for the respective programs when they click these links. Unfortunately, these seemingly legitimate download URLs are part of a malicious scam that infects victims with BlackCat/ALPHV ransomware. Visitors from particular geographic locations are directed to phishing sites where they can download malicious DLL files via trojanized ISO installers. A msi.dll called NitrogenInstaller installs the Nitrogen initial access malware and a malicious Python application. It also creates the registry run key Python for persistence and runs a malicious Python program once every five minutes. Furthermore, NitrogenStager is executed by the Python component, which establishes communication with the threat actor's C2 and launches a Meterpreter shell and Cobalt Strike Beacons. Since NitrogenStager cannot execute Python scripts, attackers engaged in hands-on action after executing the Meterpreter script, downloading additional ZIP files and Python 3 environments to launch Cobalt Strike in memory.