Description

A fresh and enhanced version of the DarkCloud information-stealer malware is attacking Microsoft Windows platforms, according to Fortinet's FortiGuard Labs in July 2025. This is a high-severity attack campaign, which employs advanced phishing tactics, usually in the form of a RAR file that pretends to be an urgent quote with no message body to arouse user interest. When it gets extracted, an JavaScript file runs obfuscated PowerShell code, which downloads a JPEG file with an encrypted .NET DLL. This DLL is loaded reflectively and employed to create system persistence through auto-run registry keys, and to trigger the payload through process hollowing of a suspended MSBuild.exe process. The stealth features of malware are fileless execution, anti-analysis and sandbox evasion capabilities. DarkCloud, developed in Visual Basic 6, decrypts over 600 runtime-encrypted strings and remains inactive until detecting genuine user activity through the GetAsyncKeyState() API. Once installed, it harvests sensitive information like browser credentials, credit card info, system data, email addresses, and data from utilities like FileZilla, Thunderbird, dnSpy, and Wireshark. Browser information is obtained from SQLite databases and decrypted using an auxiliary executable, in addition to system and public IP information being logged. For exfiltration, stolen data is transferred by SMTP through the use of decrypted server credentials to send the files via TLS emails, hiding the communication to evade detection. The attack is highly threatening to individuals as well as organizations. Fortinet prevents the threat through AntiSPAM, Web Filtering, IPS, and AntiVirus services with detection signatures such as `JS/DarkCloud.ACVJ! tr` and `W32/DarkCloud.QU! tr`.undefinedUsers should strongly be advised to turn on real-time protection, keep their systems updated, and engage in security awareness training to ensure they are not vulnerable to such fraudulent phishing campaigns.