Ghostwriter Targets Ukraine Government Entities with Prometheus Phishing Malware

Ghostwriter, a Belarus-aligned threat actor, has targeted Ukrainian government organizations using Prometheus-related lures. Phishing emails are sent using compromised accounts and have been active since spring 2026. The emails typically include a PDF attachment that links to a ZIP archive containing a JavaScript file named OYSTERFRESH. OYSTERFRESH shows a decoy document while stealthily writing an obfuscated and encrypted payload called OYSTERBLUES into the Windows Registry. It also downloads and launches OYSTERSHUCK, which decodes OYSTERBLUES. OYSTERBLUES collects system information such as computer name, user account, OS version, last boot time, and running processes, then sends it to a command-and-control server via HTTP POST. The malware then receives next-stage JavaScript code and executes it using eval(), with the final payload assessed as Cobalt Strike. CERT-UA recommends restricting wscript.exe execution for standard user accounts to reduce attack surface.

"Typically, the email contains a PDF attachment with a link that, when clicked, leads to the download of a ZIP archive containing a JavaScript file. The JavaScript file, dubbed OYSTERFRESH, is designed to display a decoy document as a distraction mechanism, while stealthily writing an obfuscated and encrypted payload called OYSTERBLUES to the Windows Registry, as well as downloading and launching OYSTERSHUCK, which is responsible for decoding OYSTERBLUES."

"OYSTERBLUES is equipped to harvest a wide range of system information, including computer name, user account, OS version, time of the last OS boot, and a list of running processes. The collected data is sent to a command-and-control (C2) server over an HTTP POST request. It then awaits further responses containing next-stage JavaScript code, which is executed using the eval() function."

"To reduce the likelihood of this cyber threat being exploited, it is advisable to apply known basic approaches to reducing the attack surface, specifically by restricting the ability to run wscript.exe for standard user accounts."

"The activity, per the Computer Emergency Response Team of Ukraine (CERT-UA), involves sending phishing emails to government entities using compromised accounts. It's been active since the spring of 2026. The Belarus-aligned threat actor known as Ghostwriter (aka UAC-0057 and UNC1151) has been observed using lures related to Prometheus, a Ukrainian online learning platform, to target government organizations in the country."

Read at The Hacker News