APIs

A new wave of ClickFix attacks has emerged, using fake Windows Update screens and PNG image steganography to deploy infostealing malware like LummaC2 and Rhadamanthys. The attacks trick users into executing a command by pressing Win+R and pasting a command copied to their clipboard. Attackers have shifted from using “Human Verification” lures to more convincing full-screen fake Windows Update screens. The fake update prompts users to run a command that initiates mshta.exe with a URL containing a hex-encoded IP address, leading to the download of obfuscated PowerShell and .NET loaders. A notable feature of the campaign is the use of a .NET steganographic loader that hides shellcode within the pixel data of a PNG image, which is decrypted and reconstructed in memory. The shellcode is Donut-packed and injected into processes like explorer.exe using standard Windows APIs. Huntress has been monitoring these ClickFix clusters since early October, noting the use of the IP address 141.98.80[.]175 and various paths for the initial mshta.exe stage, with subsequent PowerShell stages hosted on domains linked to the same infrastructure. Despite the disruption of Rhadamanthys’ infrastructure in mid-November, active domains continue to serve the ClickFix lure, although the Rhadamanthys payload appears to be unavailable. To mitigate the attack, disabling the Windows Run box through Group Policy or registry settings is recommended, along with monitoring for suspicious activity involving explorer.exe. User education is critical, emphasizing that legitimate processes will not require pasting commands into the Run prompt. Analysts can check the RunMRU registry key to investigate potential ClickFix abuse.