ClickFix Phishing Campaign Masquerading as a Claude Installer

Overview It is no secret that phishing campaigns utilizing various ClickFix techniques have been a commonly used method of social engineering . One of the main reasons for this is simply because they work. You know this and Rapid7 does as well. As a company offering managed detection and response (MDR), our customers expect us to be knowledgeable about and able to detect attacks as common as ClickFix campaigns. Recently, Rapid7 observed a small grouping of ClickFix events across customers in the EU and US. At the time of discovery, this campaign had very little traction on sites like VirusTotal or within the online security landscape. This campaign was particularly interesting as it appeared to be masquerading as an installer for Claude, an AI tool that has received a considerable amount of attention. Using Rapid7 InsightIDR detection rules, our SOC analysts were able to detect and respond to the threat, preventing further compromise. This campaign demonstrates the strength Rapid7 customers get from our MDR service, while peeling back the curtain to provide a real-world example on how we operate behind the scenes. In this blog, we will detail a brief technical analysis of the observed threat actor activities and discuss how this serves as an example of the service we aim to provide our MDR customers. The analysis highlights both the multi-step delivery of the payload as well as the work Rapid7 performs when investigating threats. Observed attacker behavior On April 9, Rapid7 was alerted to mshta executed on a customer asset using the Windows run utility. The alert was generated by the detection rule Attacker Technique - Remote Payload Execution via Run Utility (shell32.dll) . This rule will generate an alert when a suspicious process, such as mshta, is added to the RunMRU registry key. This key is important for the detection of ClickFix campaigns, as it tracks the last 26 commands executed by the Windows run utility. One thing that stuck out about this particular mshta command is that the URL, download-version[.]1-5-8[.]com/claude.msixbundle , appeared to be impersonating an MSIX bundle for the popular AI tool, Claude. MSIX files are Windows app packages that one would typically see from the Microsoft store, definitely not something you would see being passed as an argument to mshta. While the host was quickly taken down before Rapid7 was able to obtain the claude.msixbundle payload, a copy was obtainable on VirusTotal. Looking at the payload, it does initially appear to be an MSIX bundle. The file header signature, PK, indicates that the file is a ZIP archive and contains a string reference to the MSIX bundle, MicrosoftBing_1.1.37.0_ARM64.msix : ⠀ ⠀ Exploring the payload deeper, however, reveals an HTML Application (HTA) embedded within the ZIP archive: ⠀ The Visual Basic script within the HTA file contains a series of obfuscated strings that are deobfuscated with the following VBS function: ⠀ Additionally, one of the functions serves to generat